This short book was written some years ago and is therefore somewhat out of date. My intended readership was mainly farmers looking at the potential of farming more organically, not necessarily converting their production system to a fully certified organic one. It was only partially completed and never proofread by others and so will contain inevitable errors. Nevertheless it may contain something of interest to the reader. I invite comment now as I anticipate finishing the book in the not too distant future.
Market Potential for Organic Produce
In the late 1980s, the demand for organically grown food in Australia was accelerating dramatically. In Melbourne the market doubled in a period of twelve months. The recession hit the organic food industry later than most and had a less severe impact. As we are slowly leaving the recession behind, demand is once again strengthening. Domestic prices are predicted to remain firm for a long time as European, Asian and North American demand for Australian organic produce is strong. Current organic production is estimated to be worth around $168 million annually. This compares with the stone fruit industry ($168 million), the rice industry ($183 million) and the egg industry ($278 million).
Opposite are the contents of a fax received from Ian Diamond of the organic export company, The Organic Connection. Note that these are existing customers. Tasmanian cherry grower, Peter Windhurst and Victorian garlic grower, Phil Ward, travelled to Asia in 1993 to assess markets there. It appears likely that demand for organically grown produce will outstrip supply for the foreseeable future.
Many farmers have looked with envy at these sorts of figures, but it must be realised that the higher prices received for organic produce do not necessarily translate into higher incomes. Organic farmers often claim that they are justified in charging a healthy premium as their costs are high. There is precious little information on income from organic farming versus conventional, but it is significant that farmers who convert to organic almost never go back to conventional farming. I know of only one. Els Wynen and ? Edwards’ study of sheep/wheat farms in South Eastern Australia showed that there was no statistical difference between conventional and organic farm incomes. Many organic farmers have sold their produce into the conventional market for decades.
One of New Zealand’s largest companies, Watties Frozen Foods, is one of only three certified organic frozen vegetable producers in the world. Their technical specialist in organics, Alec McErlich, agrees that despite the premiums of 20 to 310% that they are paying growers, the farmers’ incomes are on a par with conventional growers. After only three years, they have 30 farmers under contract, 20 of them new to organic production. Even though it is early days, the company expects to process several thousand tonnes of organic peas, beans, sweet corn and carrots for export in 1993/4.
Organics not the Only Option
When this book was first conceived, it was about conversion to organic farming. Several years later, it has evolved into more than that. It is more a book about common-sense farming. There is a spectrum between those who believe that you can’t grow crops without artificial fertilisers and pesticides at one end and those who believe artificial fertilisers and pesticides are poisonous at the other. These ideologies are only tenable if you ignore some of the facts about plant and animal nutrition. Facts are stubborn creatures that long outlive theories, or ideologies. Many farmers are becoming disillusioned by conventional farming advice to do “more of the same” when confronted by seemingly intractable problems and are discovering that what works for organic farmers also often works for them.
We cannot claim that organic techniques are a panacea for all farming ills. We do claim that many problems are caused by so-called solutions to other problems.
While this book will be invaluable for those farmers looking to convert all, or part of their farm to organic, it will also discuss some of the shortcomings of full organic production, as well as the shortcomings of conventional production. In the pursuit of increasing crop yields and short-term farm profits, several other issues have been neglected. The first and most obvious is the degradation of the land. The others include declining health of the consumers of farm produce, be they livestock, or humans, and a long-term decline in farm profits. Organic technologies address all of these issues.
The writer has developed his ideas over a twelve year period of running a smallholding growing vegetables and apples, keeping goats, sheep and laying hens. For five years he provided consultancy to conventional growers converting to organic production and for twelve months was a partner in a business selling organic fertilisers to conventional farmers. For several years he was a director on the board of the National Association for Sustainable Agriculture, Australia Ltd and he has delivered papers on organic production to the Australian Institute of Agricultural Scientists and the Australasian Plant Physiologists Society among others.
Most of the information for this book came from personal experience and the experiences of successful farmers. A smaller amount came from the work of agricultural academics and historians. It is the writer’s observation that the most useful academic information has come from writers who were brought up on farms, or who were successful farmers at some time in their career. Farming is a business intended to generate a profit. Any reasonable business must be capable of generating profit indefinitely and it was the pattern of decreasing profit in conventional agriculture that gave rise to the desire to help farmers improve their agricultural and economic sustainability.
The writer’s good friend and colleague, Tim Marshall, was a founder of the National Association for Sustainable Agriculture, Australia Ltd. He says that we currently don’t know what makes a sustainable agriculture. We do know that conventional agriculture as it is currently practised is not sustainable; it is totally dependent on limited fossil inputs, coal, oil, gas and phosphate rock. We know that organic agriculture has certain characteristics that indicate it to be more sustainable than conventional, so it is plain common-sense to start the investigation there.
The proponents of conventional agriculture like to perceive themselves as scientific and the practitioners of organic agriculture as unscientific. In fact, as Tim points out, there is good science and bad science. When the results of bad science are discounted, what remains points to the organic approach as often (but not always) being more scientifically sound than many (but not all) conventional practises. Both Tim and I expect to see agriculture settle somewhere between the two extremes.
It is worth remembering that 95% of what organic and conventional farmers do is the same. They all use tractors, spray equipment, seeders, manure spreaders, storage sheds and so forth. Their produce is harvested and marketed and at the end of the financial year, profits and losses assessed. There are organic farmers in every agricultural pursuit except tobacco.
You will often read, or hear, many myths about sustainable agriculture and organic farming. A study of low input sustainable agriculture (LISA) farms in the United States demolished more than a few. The study showed 70.9% of conventional farmers believe that yields will fall without chemical inputs. The response of LISA farmers was that 35.3% said yields had fallen, 17.6% that yields had increased and 47.1% that yields remained the same. The percentage of conventional farmers saying that fear of lost profits prevented them from reducing chemical inputs was 63.8%. Lower yields cut profits for 33% and 76% said that lower costs had increased profits. In the final analysis, profitability comes from good farm management and too often, chemicals are used as a substitute. This book will hopefully help improve your farm management.
Farming is moving from its previous obscurity in the public eye and the public is holding farming accountable in the same way it is holding other industries accountable. The effects of farming are not limited to the farm; soil degradation, salination, spray drift and rural tree decline affect us all. We may choose to agree, or disagree with these issues becoming matters for public debate, since it impinges on what many farmers perceive as their freedom. But just as we, as farmers, take serious affront at damage to our farms from industrial pollution, government intervention (or none-intervention) and bank policies, the public has every right to demand that we maintain the land in useable condition and refrain from practises that have undesirable off-farm effects.4 The industrialisation of farming can be seen, in retrospect, as a failure on several counts. It has caused families of many generations to leave the farms they loved. It has resulted in others having their farms locked-up for production purposes due to apparently permanent contamination with persistent pesticides and their residues. More importantly, it has deferred problems for the future to solve (and pay for) in return for short-term profit. Perhaps unfortunately, the future has arrived.
One of my friends in the upper echelons of a state agriculture department commented that disasters such as Bhopal and Chernobyl might turn out to be beneficial, in that they occurred while there is still time to do something about preventing worse disasters. The Bhopal calamity in India when a fault at the Union Carbide Plant resulted in the leaking of poisonous gas (a commonly used agricultural pesticide) into the atmosphere killing over 2,000 people and seriously incapacitating tens of thousands, alarmed many people. In Michigan in 1973, a large chemical firm which manufactured highly toxic chemicals as well as a livestock feed additive, cross-contaminated the products. As a result, an extremely dangerous halogenated hydrocarbon was included in the feed supplements of animals on over 500 farms. By May 1975 16,000 cattle, 3,000 pigs, 1,200 sheep and 1,500,000 fowls had been quarantined and later destroyed. Despite this action, the chemical substance (which in humans causes a variety of health problems) was later found in food for human consumption. The chemical, which is stored in the fatty tissue of animals as well as humans, was absorbed by an unestimated number of people. Compensation claims have been enormous, as have the environmental and other effects.
This is not a manifesto for returning to pre-industrial agriculture. We can never return to the past, no matter how much some may wish we could. Post-industrial agriculture, like post-industrial industry, politics, economics, society, communications and everything else, is in the making. While we are clearly leaving some things behind, the future is far from clear. Just as Jethro Tull and his revolutionary horse-hoeing husbandry was at the junction between the agrarian and industrial ages, we are a society in transition. We are witnessing the failure of all of our institutions to cope with modern circumstances.
The crises that beset us today are global in scope. No national government appears to have made a significant effective decision that has had the intended outcome for at least a decade. This is not the fault of our political leaders, or bureaucracies. The systems they work with were designed three centuries ago and are merely showing their age. Back then, there were no businesses spanning the globe with individual budgets that are larger than the budgets of most nations. There was no instantaneous satellite communication, mass media, or mass transport.
We are truly entering a new era. While stubborn old facts remain the same, the way they are interpreted for human use is changing rapidly. Farming, as the essential human occupation, is also changing. We can perceive this as a threat and fight to maintain the status quo (a dubious position given recent trends in farm incomes), or face the prospect of change as a challenging opportunity. I have few answers, but many questions. This book contains many facts and some speculations about how Australia’s farmers can seize the opportunities that are presenting themselves. It is my hope that the readers of this book will find it of use in formulating their response to the challenges that lie in the present and near future.
Eliot Coleman says that agricultural scientists want to know why, that farmers want to know how. What is often left unsaid is that the scientist looks for the why in what the farmer has observed. Conversely, many farmers are unhappy unless they know the why of what they do. Part of this book is concerned with the why and part with the how.
I apologise in advance to some of my readers for occasionally becoming too technical for them in places. I have tried to keep this to the minimum necessary to forestall some of the criticism from those who still perceive the organic approach to farming as merely “muck and mystery”. For reasons that are not entirely clear, the facts of organic farming are often denied by the agricultural scientific establishment. Most of us have no grasp of the quantum mechanics in nuclear bomb, or computer design, but this does not lead us to deny the existence of nuclear bombs and computers. Organic agriculture, unlike other pursuits, seems to attract criticism (and advocacy) by people with any degree of ignorance.
Primarily, this book is intended for the practical farmer, though it is anticipated that the readership will be much wider.
A Brief History
Our agricultural crops illustrate the fact that an evolution of species for speculative economic values only through man’s management has increased pests, diseases and extinction rather than their healthy and fecund survival. — William Albrecht
There are more definitions of organic farming than there are organic farmers; chemical-free, spray-free, natural, ecological etc. This is as much due to unawareness of the history of farming as it is of organic farming practises themselves. Understanding the forces that gave rise to several different approaches to crop production and animal husbandry in turn gives rise to the realisation that there can be no simple definition of such a complex activity.
Let us first put farming where it belongs. It is the single most important pursuit of humankind. Without farming, we would have insufficient food, clothing and shelter to support the world’s population. Without farming, there would be no cities, civilisations or computers revolutionising the way we perceive the universe and communicate with each other.
In the beginning, we had hunter-gathering. Humans lived in small nomadic groups scattered over large areas. Until recently, it was believed to be a harsh existence of unremitting toil. Accurate anthropological observation of the few remaining hunter-gatherer societies does not support this view. It is apparent that such groups spent only a small proportion of the day obtaining food. The balance between the population and food supply was maintained not just by nature (disease, death from predators, drought-induced famine etc), but also by human intervention. For instance, excess female infants were killed.
This method of population control existed until quite recently in agrarian societies. Some societies practised it directly by slaughtering newborn daughters until a son was born. Later, this developed into women explaining away the death of a female infant by starvation as, “it was sick and wouldn’t eat”. While the feminist movement would have us believe that this was a system devised by men for the oppression of women, it was in fact an essential part of the fabric of a society that of necessity lived within the limits of its resources.
In hunter gatherer societies, there was a division of labour between male and female. The men hunted for animals, the women gathered wild fruits, vegetables and grains. From this observation, it seems likely that agriculture, the controlled growing of fruit, vegetables and grains, was invented by women. This most important development some ten thousand years ago, was the dominant force in human progress until three hundred years ago. Population growth beyond the limits that Nature set had become possible.
Men, however, were still hunters. When they were not sharing the labour of working in the fields, they managed to hunt several species of animal to the point of extinction in more settled areas, such as Britain. These species included wolves and bears. It is interesting to note that there is no recorded human death caused by a healthy wolf in the history of the United States following European settlement. Clearly, hunting was performed more for cultural reasons, rather than food, or safety.
There is a belief, or assumption, that agriculture was an unmitigated success. Unfortunately, we can see from looking at its birthplace, North Africa and the Middle East, that it has left devastation in its wake. Humankind had gone from a belief that Nature set the limits, to a belief that those limits could be expanded by human activity. When the population of Mesopotamia expanded to the limit of the agricultural food supply, irrigation was introduced to increase the amount of food. This eventually led to the birth of a desert and the demise of agriculture in that region. It looks ever more likely that the Sahara, the largest desert on the planet, was at least partially created by human agricultural activity.
The solution devised to overcome this problem was migration. Much of recorded history is an account of migration, caused by both population pressure and the need for finding replacement for worn out land. In Roman times, Israel was “a land flowing with milk and honey” and North Africa was “the granary of the World”. Both are now suffering badly from desertification.
This is not to say that all agricultural activity was so singularly unsuccessful. In southern China, there is land that has been farmed intensively and continuously for four thousand years, supporting several times the number of people per hectare than anywhere else on the planet. The Nile delta, with its annual injection of silt from the mountains of Ethiopia, remained productive for even longer. It is only the building of the Aswan dam that poses a threat to the continued fertility of the region, due to its holding back the farmland’s annual injection of fresh silt.
Until Jethro Tull devised his horse-hoeing husbandry, farming methods had changed little since Roman times. Tull’s invention of the seed drill to place cereal seeds in straight lines enabled the use of the horse-drawn hoe for weed control and a consequent increase in food production per man-hour. “Turnip” Townsend’s Norfolk four-course crop rotation reduced the amount of land in fallow and enabled more animals to be over-wintered. This too increased food and fibre production, and the population of Britain boomed, setting the stage for the rapid expansion of industry.
The Industrial Revolution of the nineteenth century gave rise to a belief that given sufficient time, anything could be understood sufficiently well to be brought totally under man’s control. Humanity had come to the conclusion that there are no limits. As well as dramatically increasing the range and volume of manufactured goods, the Industrial Revolution gave birth to modern science. The scientist believed that simple causes only give rise to simple consequences and that complex systems are made up of a number of simple subsystems. By understanding a sufficient number of simple subsystems, a complex system could be modelled and understood.
It is only recently that these beliefs have come to be questioned. There are limits. Simple causes more often than not give rise to complex results. The sheer number of simple subsystems in large complex systems mitigates against any possibility of understanding them by fragmentary analysis. One example that comes immediately to mind is economics. Probably more effort has been put into understanding this subject than any other during the last few decades. While economics uses the tools of science, it has proved unequal to the task of predicting the outcome of political decision-making. One disillusioned economist compared our economic system and economic decisions to a man kicking a rabbit. The direction the rabbit chooses to run is unpredictable. The number of variables is just too large.
Similarly, the managed ecosystems of farms have a lamentable tendency to exhibit unpredictable behaviour. No matter how many of the subsystems become understood, the outcome of manipulating them often fails to realise expectations. Nobody in the 1950s could have predicted the economic devastation that would be caused for some Australian farmers in the 1980s by the indiscriminate use of organochlorine pesticides. The pesticides used to kill the cotton boll weevil in the Lower Rio Grande area of North America also killed the weevil’s predators. The population of two previously innocuous pests (immune to the pesticides) swelled to fill the vacancy left by the demise of the weevil and consequently made cotton growing impossible in the region.
Consequences such as these can take years to reveal themselves, sometimes long after the original cause has been forgotten. While the catastrophic result of the Lower Rio Grande is obvious, more subtle differences can arise with lesser, but still significant consequences. Herbicides commonly used on cereal crops in the name of efficiency are known to reduce overall crop yield by as much as 30%. The herbicide glyphosate appears to inhibit trace element availability in the soil and the consequences of this are more likely to reveal themselves as nutritional problems in the consumers of the produce (livestock, or human), but that is the subject of two other chapters of this book.
There are 2,000 or so different species of microorganisms in a living soil. The exact function and purpose of only a very few have been discovered and the number of possible interactions between them boggle the mind. It looks very much like we will never be able to understand such a living system with any great precision. This is less problematic than it might seem. We are not suggesting that we throw the scientific baby out with the economic bath water. Science, within its limitations, has given us a body of data that, combined with observation of obviously successful farming systems, should enable us to improve our farming and its sustainability. We really have two choices; either we continue to ignore the effects of soil biology and the wider ecology of the farming environment, or we accept that they are a vital component of farming.
One myth that really needs debunking is the belief that organic farming is “chemical-free”. There are many chemicals used by organic farmers, including copper sulphate (bluestone), phosphorous acid, sodium silicate (waterglass), soap (potassium, or sodium stearate), calcium hydroxide (lime) and sodium carbonate (washing soda). The difference between these chemicals and those used by conventional farmers is that they all have been used for a long enough time for their safety to have been established beyond reasonable doubt. The issue of safety from the organic farming point of view is less one of safety for the farmer, or consumer, but one of safety for the biological systems on which the organic farmer relies and the conventional farmer has been taught to ignore.
There is a widespread belief that organic farming is conventional farming minus the chemicals and artificial fertilisers, natural materials substituting for both. While pyrethrum is a natural pesticide, just like the synthetic malathion, its effects are not confined to the target pests. Both biocides kill predators and pests indiscriminately. Consequently, the use of either disrupts the balance between pest and predator, leading to an enhanced environment for pests at the expense of predators. I am not arguing here for the elimination of pyrethrum from the list of organically acceptable inputs, but for a better understanding of the consequences of pesticide use, synthetic or natural.
The public perception of organic farming being chemical-free has led to increasing demand for organic produce in the belief that it and the organic production system are chemical-free. The organic movement, by perpetuating this myth, has diminished its credibility. Many modern agricultural chemicals degrade rapidly, particularly in an environment conducive to microbiological proliferation. While research in this area is in its infancy, there now appears to be a distinct likelihood that conventional farming can deliver produce at least as “clean” as organic farming production standards demand. The Green Movement, by promoting the desirability of chemical-free produce and the Organic Movement, by accepting this, have completely missed the point of the organic farming technology developed since the turn of the century. A little more history will clarify this.
The great German chemist, Justus von Liebig, applied his considerable intellect to understanding plant nutrition. He discovered through many pot trials that plants depended on a handful of elements in the soil, most notably nitrogen, phosphorus and potassium. Furthermore, he discovered that he could feed these substances to plants in water-soluble form and achieve yields much higher than usual.
Liebig postulated that the element in shortest supply was the limiting factor in crop yield and that all of the elements removed with the crop must be replaced. These simple, common-sense concepts have been taught in agricultural and horticultural institutions ever since. Shortly before he died, Liebig wrote about his later discovery, his theory did not work out in practise. Unfortunately this work has never, to the best of my knowledge, been translated into English.
The barrel shows Liebig’s theory diagrammatically. If the potential yield of the soil is represented by a full barrel of water and the individual staves the quantity of individual fertility elements in the soil, then the barrel can only be filled to the height of the shortest stave.
Following the publication of Liebig’s ideas on crop fertilisation, John Lawes invented what he called superphosphate. He discovered that turning animal bones into fertiliser with sulphuric acid was much less expensive than grinding them up, since sulphuric acid was a cheap by-product of the Industrial Revolution’s chemical industry. This acidified phosphate gave crop yield increases for little financial outlay. When the supply of bones became insufficient, rock phosphate, the petrified residues of bird excreta, was an even cheaper substitute. Interestingly, Lawes’ original directions for using superphosphate recommended reverting it with lime to neutralise its acidity.
The second major impact of modern industry on agriculture came after the First World War. The conflict gave rise to a big demand for explosives based on nitrogen. Large factories were built to convert atmospheric nitrogen into ammonia and nitrates. When the battle ceased, there was an understandable reluctance to cease production. Although it was “the war to end all wars”, the potential for future conflict meant that the factories needed to remain productive. The factories were converted to nitrogenous fertiliser manufacture which made the shareholders happy and governments feel more comfortable.
The two decades between the First and Second World Wars is when the revolt against scientific agriculture began in earnest. Scientific agriculture was seen by certain farmers to have lost something in the pursuit of increased production. Animal health was in decline with new diseases and crop health also was suffering from new pests and diseases. Lucerne fields that had yielded well for decades needed to be ploughed up and resown after less than ten years. To some farmers and scientists this was a clear indication of the failure of modern, intensive methods of production. To others, it was a marketing opportunity to sell “cures” for these problems.
In India, Sir Albert Howard was studying the role of certain fungi and humus (compost) in plant health. This work gave rise to a concept he called organic farming. This wasn’t simply a return to the conventional farming of the past, but built on new concepts of plant nutrition and the relationships between crops and livestock. “Progressive” farmers were simplifying their farms, after the fashion of factories; artificial fertiliser inputs at one end and produce and “waste” coming out the other. Howard believed there was more benefit to be gained from using animal manures and crop residues to build soil fertility. The concept of the organic farm included that of mixed farming, where the byproducts of one part of the farm were the inputs for another. Rather than burning straw, it was used as animal bedding. The mixture of dung and urine-soaked straw was then composted with crop residues to become fertiliser for crops.
Howard had found that some plants he was studying relied on a symbiotic root fungus (mycorrhiza) for their phosphorus needs. In return for supplying the plant with phosphorus, the fungus took its carbohydrates from the plant. These fungi needed particular soil conditions for their survival and the plants on which they thrived often required the fungi for their survival. The soil conditions they favoured were high in humus and biological activity. The source of humus was decomposed crop residues and animal manures, the very materials that factory farming was assiduously burning, or dumping, often in the belief that they were a source of disease.
Howard further discovered in his experiments with humus manufacture and use (composting), that its presence in the soil conferred many benefits. Perhaps the most important from the point of view of the farmer beset by pests and diseases, was the relative absence of these problems in compost-grown plants. Tomatoes grown with compost were more resistant to Tobacco Mosaic Virus (TMV). Plants infected with TMV were placed among the plants in the trials. Even tomatoes grown using compost made from plants infected with the disease were unaffected.
When Howard was eventually allowed to experiment with feeding compost-grown crops to cattle, he found that they were resistant to infection by foot and mouth disease, even where infected cattle were allowed to rub noses with those in his feeding trial. It must be pointed out that the strain of FMD was much less virulent than that which caused so many problems to British farmers in the 1960s.
Howard returned to England and began publishing his ideas. They gave rise to the Soil Association which he co-founded with Lady Eve Balfour. The Soil Association was formed to scientifically investigate the differences between scientific and organic agriculture. This work was published in Balfour’s book, “The Haughley Experiment” which these days is printed as a single volume with her earlier book, “The Living Soil”. The work at Haughley clearly showed marked differences between systems that used chemical fertilisers, with or without crop and animal manure residues. Although chemical fertilisers increased grass yield, the output of milk per cow was less. Crop yield increases were insufficient to pay the cost of the artificial fertiliser used. One anomaly that showed up was egg production appeared to be dependent on amount, rather than quality of feed.
In Germany, Rudolf Steiner founded a school of philosophy, Anthroposophy. Some of his followers were farmers and they brought their agricultural problems to Steiner for his advice. In response, he eventually gave them a series of lectures published in his book, “Agriculture”. This farming system he named Bio Dynamic and it bears more than a passing resemblance to Howard’s organic farming with a similar emphasis on humus. It differs however in taking account of cosmic and spiritual forces, as well as the influence of soil. The association with spiritual beliefs and astrology has limited the appeal of Bio Dynamics for scientists trained to ignore what it automatically calls pseudo-science. Nevertheless, several respected scientists have pursued the concepts Steiner introduced, particularly in Germany.
In the United States, Dr William Albrecht took a different approach again. He was head of the Missouri Agricultural Research Station for several decades and he published an enormous number of papers about his ideas of plant nutrition and animal health. He took considerable pains to distance his work from that of organic and Bio Dynamic researchers.
The basic precept behind Albrecht’s work was that there should be an explanation for why stock health was observably superb in some regions and poor in others. He conducted extensive soil testing in various parts of the United States and found a correlation between the ratios of certain elements in the soil and protein content of the plants growing in them. When the mineral balance in a poor soil was adjusted to equate with that of a good soil, protein content of crops increased and animal health improved. He further discovered that water-soluble fertilisers were inferior to simple crushed rocks containing the required minerals.
Albrecht was also keenly interested in the effects of farming on human health. Having discovered that the prairies of the mid-west produced the healthiest livestock, he postulated that human health in this region should, in turn, be better. Since good health was a prerequisite for acceptance into military service, he perused the army intake records for the various regions of the United States and indeed confirmed his suspicion. The rejection rate for army service was lowest where soil fertility was highest and highest where soil fertility was lowest.
In more recent time, Professor Miguel Altieri at the University of California has worked on the role of ecological diversity in reducing pest problems in organic and peasant farming. He coined the term agroecology for this work.
Although there were other workers looking at alternative methods of crop production and animal husbandry, these four schools have been the most important in shaping Australian organic production methods. The first three had very little influence on the wider agricultural community when they were being devised. However, post World War Two events gave them the impetus they needed to the point where they, and Altieri’s agroecology, are now considered seriously.
The development of “cures” devised to overcome pests and diseases gained a significant boost from poisons developed as nerve-gas during World War II. Rather than storing the materials that remained unused, they were converted into pesticides and fungicides. Again, the chemical companies’ shareholders were happy to see these by-products of plastics and drug manufacture sold at a profit, rather than being stored at great expense. Governments were pleased to see them dispersed, instead of being dangerous sources of chemical pollution.
Like their predecessors, these materials had the property of only working for a short time until the pest, or disease evolved resistance. One class of pesticides though, created problems that still bedevil agriculture; the organo-chlorines. The organo-chlorine pesticides include DDT, dieldrin and heptachlor. They, or their breakdown products, are all very stable materials that accumulate not only in the organism consuming them, but also their predators. Animals high on the food-chain accumulate the most. Bird populations were decimated by these pesticides since they fed on the insects that had been sprayed. The accumulated organo-chlorines inhibited the formation of eggshell.
Somewhat paradoxically, birds are a most effective (and under-appreciated) control on many insects that compete with humans for food. Their decline led to increasing pest problems and a consequent “need” for ever more potent insecticides in ever increasing quantities. The impact of their use on Nature enraged conservationists and Rachel Carson’s book, “Silent Spring” is their manifesto.
Since the alternative agricultures all severely reduced the need for these chemical inputs, they were perceived as “a good thing” by conservationists. This is where the concept of organic equating with chemical-free arose. Bio Dynamic practitioners like to promote themselves as the purest of the pure, however Pfeiffer’s book “Weeds and What They Tell”, published in the 1940s by the US Bio Dynamic Association, advocated the use of the herbicide 2-4D. While the promotion of the desirability organic farming by the conservation movement has led to wider acceptance of organics by the general public, there is a downside. The conservation movement’s propensity for overstating the case and downright misinformation when it suits their purposes, has acted as a brake on the acceptance of organics by the wider farming community and agricultural scientists.
In actuality, many organic farming practises have already entered the mainstream of farming, especially when they have been presented without reference to their origins. It is in anticipation of an acceleration of this trend that this book has been written. The general public is demanding that agriculture become cleaner and greener. As well, there is a trend away from tough, flavourless produce that transports and stores well and merely looks good, toward tastier food. The assumption that organic production methods result in produce with poor appearance is a misconception fostered by the manufacturers of chemical agricultural inputs on the one hand, and the conservationists who believe organic agriculture is conventional agriculture minus the chemical inputs, on the other. Not only is agriculture a spectrum, organic agriculture is a sub-spectrum of its own. There are anti-chemical extremists who will brook no use of any artificial substance and growers who are more concerned about the economical production of quality produce and minimising any negative impact of their farming on the wider ecosystem.
In our investigations of agriculture, we have found many fine organic practitioners who achieve results equal to, and often better than, their conventional counterparts. That is not to say that this is universally possible. In southern Tasmania for instance, we have almost no codling moth problem in apple production. This is not the case in the warmer Australian mainland apple producing districts. It would be foolish to assert that what works well in one district will work equally well in others. While no black spot fungus was apparent in the Orange district of NSW in the summer of 1982/3, it was only kept under control in southern Tasmania with chemical inputs. It is worth noting here that sodium silicate (waterglass), which is an organically acceptable chemical, gave results equal to the more potent modern fungicides. Dr James Wong’s research using calcium hydroxide also showed the potential of this chemical to substitute for a large part of the usual spray program.
Prices for some produce are kept artificially low with hidden costs; wheat, for instance. The Soil Conservation Authority estimates that each kilogram of wheat grown in Australia costs as much as five kilograms of topsoil lost to erosion. Such waste of non-renewable resource obviously cannot continue indefinitely. There is considerable resistance to the introduction of soft wheat in Australia. We are justifiably proud of the reputation of our hard wheats that are necessary for bread manufacture. The soft wheat variety, Longbow, out yields hard wheat by a factor of several times. Products other than bread that use wheat as an input could be reduced in cost by the use of this variety with no discernible difference in quality. A move to this wheat variety would allow less land to be used for the crop and more for growing green manure.
The following chapters describe various techniques used in organic farming and the reasons why organic farmers generally have less problems with pests and diseases than their conventional counterparts. We also assess the shortcomings of the various organic certification scheme requirements in the real world of mass production. While it is certainly true that conventional farming’s sustainability will benefit enormously from understanding the concepts behind organic production, many organic practitioners and their proponents could learn a lot from a genuine understanding of modern crop production requirements.
It is the writer’s fond hope that when he becomes a doddering old fool sitting by the fire with his glass of port, that we will talk not of organic versus conventional agriculture, but only good farming practises.
The products of agrotechnology are displacing the source upon which the technology is based. It is analogous to taking stones from the foundation to repair the roof”. — Garrison Wilkes
The major difference between the two extremes of modern agricultural practise lies in the attitude toward soil. The chemically oriented extreme sees the soil as merely an inert medium to hold up the plants that grow in it. Taken to its utmost, the soil is eliminated, as in hydroponics. The organic extreme sees the soil as the only proper source of plant nutrients and that nothing should be imported onto the farm, or sprayed onto the crop. The vast majority of farms operate somewhere between these limits.
There are now few agronomists who would argue with the proposition that a high level of organic matter in the soil is desirable from several points of view. The first is that soil well-supplied with organic matter is easier to till. As organic matter levels in the soil have declined, tractor power needed to increase to achieve the same amount of work. As well, organic matter is a sponge for water, the major crop-limiting factor. Not only is organic matter a source of slow-release nutrients, it also can have the capacity to hold on to nutrients that were not an original component of the organic matter. Such a soil has its constituent particles held in aggregates, called crumbs. The air gaps between the crumbs allow better aeration, more rapid infiltration of water and better drainage.
Organic matter in the soil takes several different forms. The most important from the point of view of farming are humus and its related compounds. Organic matter in the soil can remain undecomposed, ferment, or humify. Raw organic matter ties up nutrients in a form that plants cannot access until it has decomposed. Fermentation results in the production of alcohols and other substances that inhibit plant growth. Humification produces the essential materials that qualify soil as fertile.
The factors that promote humus formation are: a source of lignin, cellulose, a nitrogen source, water, warmth and oxygen. Lignin and cellulose are the structural part of plants. The lignin component is transformed by bacteria into humus. The cellulose is the energy source for those bacteria. The nitrogen is required for the formation of the bacterial protein. If this nitrogen is already in the form of protein, such as animal manure, or a leguminous green manure, then the humifying bacteria can use it directly. Water soluble nitrogen sources must first be converted to protein by other bacteria before they can be used. Water soluble nitrogen is not only susceptible to leaching, but also seems to promote the proliferation of undesirable fungi. Moisture levels should be those sufficient to allow plant growth. The optimum temperature range is between 15 and 25°C. Below 10°C there is very little bacterial activity. Above about 30°C humus tends to oxidise at a greater rate than it is produced. Oxygen is required by humifying bacteria. In the absence of oxygen, anaerobic bacteria and fungi decompose organic matter and this is the fermentation process that results in production of plant inhibiting chemicals, such as alcohols.
Another factor that affects humus formation is the balance of the major fertility elements calcium, magnesium, potassium and sodium. This was Albrecht’s discovery. The relative percentages to optimise humification and consequently protein formation in most crops are:
|Calcium||60 – 75%|
|Magnesium||10 – 20%|
|Potassium||2 – 5%|
|Sodium||0.5 – 3%|
|All other cations||5%|
When the soil is balanced in this way, not only is humification enhanced, but the pH (acidity) of the soil tends to stabilise between 6 and 7. This happens to be the level of acidity that optimises the availability of all the essential plant nutrients in the soil. It is also the range that is preferred by earthworms.
The role of earthworms in soil fertility cannot be ignored; their tunnels provide aeration, rapid infiltration of water and improved drainage. Their guts digest soil, some from as deep as two metres below the soil surface, releasing locked up phosphorus and a special gland secretes calcium into their casts. Some agronomists believe that man’s move from hunter-gathering to farming could not have occurred prior to the evolution of modern earthworms.
In one study of water infiltration rates, 100 mm of water was poured onto two soil samples. The sample with earthworms absorbed the water in less than a minute. The worm-free sample took more than two hours.
Earthworms also assist in restructuring soil into aggregates, or crumbs. Not only are the aggregates more prevalent in soil with good earthworm activity, the aggregates are more stable and longer lasting.
The bacterial activity associated with humification releases many essential nutrients from the silt fraction of the soil. Thirty year duration trials of soil fertilisation in Germany and Switzerland showed that, with no return of crop residues, more than 90% of the nutrients taken up by crops came from the silt, not the applied fertilisers. This research would appear to justify the claim of many organic farmers that well maintained organic farms require very little in the way of off-farm fertiliser inputs.
Silt particles, like clay, are very small indeed. Unlike clay, silt carries no negative electric charge and the particles are flattened, which is why silty soil feels silky smooth, rather than sticky like clay. Silt is created by glacial action on rocks and the bulk of the world’s silt was produced during the great ice ages. Over time, silt is depleted of its nutrients. Consequently, the young soils of the planet, such as those in Europe, are much more fertile than those of greater age, such as those in Australia. Australia is known as the “trace element desert” because of the shortage of many essential micronutrients.
Pulverised basalt and granite have been promoted as one answer to this problem. It is a relatively inexpensive material to obtain since it is a by-product of quarrying. The material must be very finely divided, to present the largest possible surface area for the bacteria to work on. You can test the potential of a sample by placing a pinch in a glass of distilled water and leaving it on a sunny window sill for a few days. The more vigorous and rapid the formation of algal bloom, the better the sample is for use as fertiliser. Some unscrupulous fertiliser companies are selling rock dust mixed with clay. While it can be said that the clay adds to the cation exchange capacity of the soil, increasing exchange capacity by increasing humus levels would appear to make better economic sense.
The Fertility Elements
We are now going to discuss the individual fertility elements, their role in plant growth and animal health, and the implications of using various fertilisers to supply them.
Phosphorus encourages root development and is essential for the formation of protein in the plant. As well, it increases palatability of the plants as it promotes the formation of fats and convertible starches. By stimulating rapid cell development, phosphorus increases the plants’ resistance to disease. Many plants respond to a phosphorus deficiency by showing a reddish, or purple colour in their leaves. Heavy feeders are stunted. Phosphorus toxicity symptoms include the margins and interveinal areas of older leaves dying. Younger leaves show interveinal chlorosis, particularly tomatoes, celery and sweet corn.
The most popular fertiliser source of phosphorus in recent decades has been superphosphate. The response of crops to super has declined over time, more and more being necessary to achieve satisfactory yields. On average, only 30% of the phosphorus in super becomes available to plants. While a tiny amount leaches out of the soil through irrigation and rainfall, the bulk is chemically locked up in the soil. Phosphorus from farmland appearing in rivers and streams is generally carried there through erosion of the soil, rather than phosphorus in water solution. Humic acids, earthworms and associated beneficial bacteria and fungi in a fertile soil unlock the phosphorus in reactive phosphate rock, chemically inactivated superphosphate and silt, making it available to plants.
Fertiliser recommendations followed by most farmers results in the application of more phosphorus than is removed by the crops. As a result, many farmers have built up phosphorus reserves in their soils that are sufficient for decades, and in some cases centuries, of cropping. Where low soil phosphorus levels are a problem, some farmers are using reactive phosphate rock (RPR) as an alternative to super. RPR is cheaper than superphosphate as well as containing a higher percentage of phosphorus and trace elements. Under typical soil conditions, the phosphorus is only readily available when the soil pH is around 4.5 to 5.5. However, the organic acids associated with bacterial activity are capable of unlocking the phosphorus when the soil pH is a more acceptable 6.0-6.5.
Many Australian organic farmers are exploiting the phosphorus residues locked up from earlier superphosphate applications. The question arises how long will those reserves last? Is there sufficient phosphorus in these residues and the silt fraction of the soil for economic, long-term production? For conventional farmers, the questions that arise are, does it make economic sense to leave 70% of the applied phosphorus in superphosphate unused? How can farmers exploit the reserves they have built up? And how long will the world’s fossil phosphate deposits last? We do not have answers for these questions at this time. Nevertheless, it should be apparent that fossil phosphate reserves will continue to dwindle, driving the price higher. As well, it would appear to be sensible to maximise the availability of any applied phosphate, rather than letting the bulk become chemically locked up to the detriment of the soil biology and the farmers’ input costs.
Nitrogen stimulates the production of plant tissue and influences the protein content. Nitrogen applied as nitrate produces a blue-green colour in plant leaves. When applied as protein, the colour is noticeably a more golden-green. Excessive nitrate levels are associated with increased fungal disease, delayed maturity of plants and weakening of plant tissue leading to lodging. As well, nitrates in the plant sap are reduced by bacteria to nitrite which is toxic to the consumer of the plant, animal, or man. In livestock, excessive amounts of nitrite in the diet cause abortion, hay poisoning, grass tetany, and reduced haemoglobin count in the blood (anaemia). Nitrogen deficiency symptoms in crops include, edges of leaves turn brown, smaller leaves and yellow-green foliage. Nitrogen toxicity symptoms include rotting of roots and delayed maturity. Young leaves are dark green and older leaves yellow with necrotic spots.
Nitrogen, can be supplied as protein (animal manure, legume green manure, fish meal, blood’n’bone etc.), or as water soluble artificial fertiliser (Nitram, urea, ammonium sulphate etc.). While a pasture can supply its own nitrogen needs through fixation of atmospheric nitrogen by clover, horticultural crops have a much higher requirement. As little as 10% of applied water soluble nitrogenous fertilisers are taken up by the crop. The remainder leaches into groundwater and streams. While this may please the fertiliser manufacturers, it is not so great from the point of view of the farmer. As well as wasting money, adverse impacts on the environment can lead to stiff penalties.
As protein slowly decomposes, it supplies the plants with nitrogen at the rate generally needed by the crop. Leaching becomes a non-issue. Where short-term nitrogen needs are not being met by the soil, liquid fish, with, or without urea, as a foliar spray is preferable to urea alone. Foliar sprays of water-soluble nitrogen encourage fungal disease. In contrast, liquid fish has been observed to reduce the incidence of fungal disease by many farmers.
While mainstream agricultural scientists have been slow to investigate, Dr James Wong and Tony Allwright of the Tasmanian Department of Primary Industry have research under way. Hopefully, this work will provide a better understanding of the reasons why organic fertilisation reduces the ability of fungal organisms to proliferate. This should enable us to enhance the degree of control. In the meantime, we know that using organic fertilisers enhances the effectiveness of chemical fungicides as well as being a worthwhile control mechanism in their own right.
In pasture, both pelletised poultry manure and liquid fish have increased clover nodulation. This is a clear indication that the clover is fixing more nitrogen that increases the protein content of the pasture. As well, palatability is reported to increase, with more even grazing. There is a downside to this, with some graziers reporting problems with stock breaking into grazed out paddocks treated with proteinaceous fertiliser, in preference to lush pasture grown on super.
Pome fruit has responded well to foliar applications of liquid fish and liquid seaweed. Lateral growth has been good with an increase in leaf size. The leaves seemed to be somewhat thicker and glossier. Red Fujis, prone to russet, which makes them unmarketable, showed a marked decline of this problem. In the writer’s orchard, a trial of foliar applications of liquid fish as the only control for black spot was a limited success in a season of overcast, drizzly weather. Some varieties remained clean, but the less resistant varieties were a disaster.
In cropping, the pelletised poultry manure was applied at a rate calculated to supply 50% of the usual artificial nitrogen application. This rule of thumb has worked well in supplying the nitrogen needs of most crops. One grower applied a soil drench of 60 litres per hectare of liquid fish to a crop of brassicas. They responded as well as they did to artificial, even though the nitrogen content of the fish emulsion was a mere 2.8%. This anomalous result needs investigation.
Potassium is essential for starch formation in the plant and the development of chlorophyll. Unlike phosphorus and nitrogen, which are part of the structure of the plant, potassium is more of a catalyst involved in plant processes. Deficiency symptoms include lowered resistance to disease, low yields and mottled, speckled, or curly leaves, especially older leaves. Potassium toxicity symptoms include marginal necrosis on the oldest leaves and in celery, blackheart.
More and more farmers are coming to appreciate deep rooting plants to bring potassium from deep in the subsoil to supply their crops’ potassium needs. Such plants are called biological ploughs because they serve much the same purpose as a ripper, leaving deep channels in the soil when they decompose. In pasture, New Zealand graziers use chicory developed for this purpose. In China, vegetable growers use Pawlonia trees whose large succulent leaves decompose to humus when they fall in autumn. The roots of lucerne and comfrey are capable of diving two metres or more into the soil.
Potassium is used to excess in many crop fertiliser programs. For instance, the recommended application rate on potatoes is twice the amount removed from the soil. This leads to reduced availability of calcium and many trace elements. As well, the most commonly used potassic fertiliser is potassium chloride (muriate of potash). This material is deadly to earthworms, as it burns holes in their skin. Frogs, Nature’s vastly underrated pest controllers, are also decimated by its use. Continual overuse of potassium chloride can lead to toxic levels of chloride and a consequent decrease in yields. Potassium sulphate (sulphate of potash) is a much better source of potassium, particularly as it includes sulphur which is often in short supply. It is unfortunate that it is much more expensive than muriate.
When the writer commenced his organic market garden ten years ago, a soil test was taken that showed a deficiency of potassium. This was “corrected” with the recommended amount of muriate of potash. In the ensuing ten years, only compost has been applied and this is regarded as only a fair source of potassium. Nevertheless, a recent soil test showed that the potassium level was slightly excessive. New Zealand dairy farmer, Brian Gordon of Katikati, had his soil tested in 1989 (see table). The recommendation from the local extension officer was the usual 300-500 kg of potash-super per hectare on his 123 hectares, plus lime. Instead, he applied 20 litres per hectare of Vitec fish emulsion annually.
As these tests show, the available nutrients in the soil increased dramatically. Taking the potassium result as an example, the increase was nearly 3,000%. The quantity of potassium applied was a mere 432 grams per hectare. If the response to fertilisers is only due to the NPK content, then the extension officer’s recommendation should have been for 1.27 kg per hectare of potash-super, not 500 kg!
These results would appear to indicate a need for great caution interpreting soil test results when introducing organic fertilisers into soils that have previously received high levels of potassium.
Calcium is often applied to the soil to release other nutrients by altering the soil acidity (pH). It is said, on this account, not to be a fertiliser. Calcium is a structural part of the walls in plant cells. As well, it is essential for the proliferation of soil bacteria. Clay soils often become sticky if there is an excess of sodium. Calcium displaces sodium attached to clay particles and since it is a much bigger atom, the clay becomes more friable. While gypsum (calcium sulphate) is recommended to break down sticky clay, it will only work if the reason for the stickiness is excessive sodium. If the soil is also acidic, it is cheaper to use limestone (calcium carbonate). An excess of calcium relative to magnesium is generally accompanied by insect problems in the crop.
Sap tests of potatoes grown on pelletised poultry manure showed much higher levels of calcium than those grown on artificial fertiliser. Part of the reason for this could well be the very high level of potassium in the artificial fertiliser. Excessive potassium is known to produce calcium deficiency symptoms in some crops. These include deformed terminal leaves, buds and branches, poor plant structure, such as weak stems, celery black heart, lettuce tip burn, internal browning of cabbages, cavity spot in carrots and bitter pit in apples.
Calcium is generally applied as ground limestone (calcium carbonate), or dolomite (a mixture of calcium carbonate and magnesium carbonate). As referred to earlier, calcium and magnesium in the soil must be in appropriate ratio. Liming to merely adjust pH will generally lead to excess calcium, or worse, if high magnesium dolomite is used exclusively, excess magnesium.
Sometimes, calcium hydroxide is used for a quick response. The bulk of this is rapidly converted to calcium carbonate when it reacts with dissolved carbon dioxide in the soil water. It is more economical to use very finely ground limestone if a faster response is needed.
When the soil is badly out of balance, it is not a good idea to lime heavily. This has a very bad effect on the soil microbiology. It is much better to apply more frequent, lighter applications.
Magnesium is the companion to calcium in mineral deposits. The carbonates of both are used as lime. However, in plant nutrition it is the companion to phosphorus and stimulates the assimilation of phosphorus by plants. It is essential for the formation of chlorophyll. Magnesium deficiency causes chlorosis in plants, analogous to anaemia in animals. An excess of magnesium relative to calcium results in too high a pH and consequent deficiency of many trace elements. In an emergency, Epsom salts (magnesium sulphate) can be applied as a foliar source of magnesium, but this is an expensive source of magnesium. Where the use of even high magnesium dolomite will still leave an excess of calcium over magnesium, there are several magnesium sources; Kieserite (16%), Magnesite (25%) and magnesium oxide (50%).
Sulphur is a neglected element in farming. This is difficult to understand as it is essential for the formation of chlorophyll, proteins and vitamins. Perhaps it is because we rely too much on research conducted in the Northern Hemisphere, where sulphur compounds generated as pollution by industry arrive in the rain. These compounds, sulphuric and sulphurous acids, as well as hydrogen sulphide (rotten egg gas), are a fortunate rarity in Australia’s relatively unpolluted atmosphere.
Sulphur can be applied to the soil as elemental sulphur. The usual source of sulphur for Australian farmers is superphosphate, which contains more sulphur than phosphorus. However, elemental sulphur is a much cheaper source when the phosphorus is not needed.
Hopefully, more work on necessary levels in the soil for particular crops will be conducted in the future. A high level of sulphur in a soil test is generally a symptom of poor soil aeration.
Trace elements are those required in minute amounts for essential plant processes. Their availability is optimised when the soil pH is between 6 and 7, the major nutrients calcium, magnesium, potassium and sodium are in balance and the soil humus level is more than 3%. Absence, or deficiency of particular trace elements may mean that enzyme cycles cannot be triggered into action, resulting in reduced crop performance, or failure. Some trace elements are required for animal and human health without having any obvious influence on plant health, or production.
The assessment of trace elements through soil testing is an uncertain procedure. Measured levels that have been thought to indicate deficiency, have been contradicted by the measurement of adequate levels in the plant tissue and vice versa. Part of the problem is the fact that certain elements stimulate, or suppress, other elements. This is an area of soil science that is very poorly understood and needs much more research. While tissue and sap testing offer the potential for better assessment of crop needs, they too have their difficulties.
Trace elements are only poorly taken up by plants when they are in salt form. This has led to increasing use of chelated trace elements. Chelation (KEY-LATION) means combined with an organic molecule. The compounds generally used are EDTA and ligno-sulphamate with the latter preferred. (EDTA is a suspected carcinogen). Of course, the trace elements in organic fertilisers, such as pelletised poultry manure, liquid fish and seaweed, are already chelated, and often these materials contain sufficient trace elements for crop needs.
Manganese is required in very small amounts and is very important, for without it, the production of amino acids and proteins suffer. It also works alongside magnesium in eliminating chlorosis. Soil with an excessive amount of magnesium and/or calcium locks up manganese.
Iron is essential for the formation of chlorophyll in plants and the prevention of anaemia in animals. Nearly all soils contain a lot of iron, mostly in unavailable form. Soils treated with excessive amounts of superphosphate often have excessive available iron, which reduces the availability of other trace elements. Maintaining good humus levels is beneficial in optimising the availability of iron.
Boron is implicated in the resistance of plants to diseases and is necessary for the formation of amino acids and protein. It is needed in only tiny amounts and many crops have benefited from the discovery that their potential was being limited by a deficiency. In the sap tests referred to earlier on potatoes grown under pelletised poultry manure, the boron levels were deemed excessive, whereas the sap tests from the conventional plot were deficient. The implications of this are unknown at this stage.
Copper, Cobalt and Zinc
There remains much to be learned about this group of trace elements. Their deficiency is implicated in a number of animal diseases, steely wool in sheep and infertility in cattle among them. Plants short of copper show abnormal growth and stunted young branches. Zinc is essential for the formation of chlorophyll, but copper and cobalt also appear to play a lesser role. Zinc deficiency is implicated in poor stock fertility.
Iodine, Chlorine, Fluorine, Sodium and Lithium
Iodine, chlorine and fluorine are all halogens. Iodine is well known as an essential ingredient in human and animal health as a regulator of metabolism. It is readily taken up by plants from foliar applications of liquid fish, or seaweed. It appears to have no major role in plant nutrition, or health.
Chlorine deficiency in plants is extremely rare. What is not rare is an excess caused by over-reliance on muriate of potash as a source of potassium. Excess chloride in soil tests is invariably accompanied by reduced availability of trace elements. Members of the rose family, rosaceae, which includes pome fruit, are particularly sensitive to excessive amounts of chloride.
Fluorine is not considered essential for plant growth, but has an important role in animal nutrition. Both an excess and a deficiency are implicated in poor tooth development.
Sodium and potassium play complementary roles in plant and animal nutrition. Where potassium is deficient, sodium is absorbed in its place. Sodium is more often in excess than deficiency. Excessive sodium makes clay sticky. Gypsum (calcium sulphate) is often used to supply calcium, which displaces the sodium, allowing it to leach, making the clay more friable. Lime (calcium carbonate) is cheaper and can also be used where an increase in pH is desirable.
Lithium needs further study, but appears to be a companion to sodium and potassium. It has been applied to tobacco crops with the benefit of improving the quality of leaf grown for cigar wrappers.
Aluminium and Molybdenum
Aluminium is known more for the toxic effects of an excess than for any role in plant or animal nutrition. The conditions leading to toxicity are excessive soil acidity, reduced aeration and biological activity and needless to say, low humus levels.
Molybdenum is essential for many plants. It serves as a catalyst in the early development of brassicas and appears to be essential in the fixation of nitrogen by bacteria. It is required in very small amounts. Deficiency is often caused by excessively acid soil and low humus levels. Excessive levels of molybdenum cause reproductive problems in livestock.
Cadmium and Lead
Cadmium and lead appear to play no role in plant nutrition, nor do they appear to be required for animal health. They are discussed here because they are toxic in excess, generally causing chronic disease, rather than outright poisoning. They are particularly problematic because the animal, or person consuming them can only eliminate them slowly. This means that they tend to accumulate in the body over time.
Superphosphate, until recently, was made from phosphate rock that was very rich in cadmium and lead. This means that soils heavily fertilised with this super contain elevated levels of lead and cadmium and it is a cause for great concern that they are taken up by crops. The level of cadmium in sheep and beef kidneys has led to their being banned for human consumption in Western and South Australia.
In animal nutrition it is known that cadmium uptake is determined by food quality. Where the diet is deficient in zinc, cadmium absorption is increased. Other predisposing factors to increased cadmium absorption include periods of low nutrient intake and lack of high quality protein in the diet.
It is a matter for conjecture at this stage, but some organic farmers believe that increasing humus levels and bacterial activity in the soil reduces the uptake of heavy metals by crops.
Enzymes are catalysts used by plants to manufacture cell tissue, trigger hormone reactions (flowering, leaf-drop etc.) and take up nutrients. Most enzymes contain a trace element. An example is the use of molybdenum by the cauliflower. The enzyme requiring this element is only created in the first few days of the plant’s existence. Application of molybdenum after this period has no effect on the deficiency symptom of “whip-tail”.
These plant hormones regulate cell division and elongation (ie. plant growth and development). They are relatively unstable and are most readily created from complex organic compounds, such as those found in animal manures, fish and seaweed. They require enzymes for their formation.
Soil acidity is the measure of the number of hydrogen ions in the soil (pH). When there are a lot of hydrogen ions, the soil pH is a low number. When there are few, the number is high. The neutral point is 7. Thus, pH less than 7 is acid, more than 7 alkaline.
Soil that is too acid, or too alkaline, locks up essential nutrients. A soil in which the calcium, magnesium, potassium and sodium are in appropriate ratio will have a pH between 6 and 7. This level of acidity is optimum for the availability of nutrients for most crops. A few crops prefer a pH between 5 and 6 and a small number tolerate alkaline conditions.
Common Commercially Available Fertilisers
Fertilisers are made soluble, but it’s a damn fool idea. They should be insoluble but available. Most of our botany is solution botany, the first rain takes out the nutrients. There’s a big difference between the laboratory and the farm. — William Albrecht
Pelletised Poultry Manure
Pelletised poultry manure, with or without additives such as fish and seaweed, is readily available and not excessively priced for use in mainstream farming when purchased in bulk. The nitrogen in fresh poultry manure is in the form of ammonium carbonate, which is caustic. Prior to the pelletising process, the manure is fermented or composted, converting the ammonium carbonate to bacterial protein. The pellets are then steam sterilised to kill any pathogenic organisms, or weed seeds.
Some growers have observed that “new” weeds have arisen following the use of this material and have believed the seeds arrived in the manure. This is not necessarily the case as the increase in biological activity, or pH change can stimulate germination of dormant weed seeds. One manufacturer makes the claim that they use only pure poultry manure, not deep litter. A sample placed in water and left overnight revealed the presence of sawdust particles. The sawdust is not necessarily a bad thing, however. The bacteria that ferment the raw manure need the cellulose in the sawdust as an energy source to convert the lignin in the sawdust to humus. There being no significant amount of lignin in pure poultry manure, there would be no humus formation when fermenting pure poultry manure. As well, much of the nitrogen that would otherwise be lost as ammonia is tied up in the humus.
Application rates for pasture are between 150 and 400 kg per hectare. The much higher rates used in cropping have created some difficulties. Modern fertiliser spreaders are built to spread low volumes of high analysis fertilisers. As well, the pelletised poultry manure takes longer to start working than artificial fertiliser and is best applied to the soil four to six weeks earlier. While banding works best with artificial fertilisers, as it “allows the plant roots to dodge them” in Albrecht’s words, broadcasting is preferred with organic fertilisers. This is because the goal is to stimulate the soil biology to release nutrients in the soil, rather than feeding the crop directly.
In two trials on peas, there were noticeably less peas left on the ground following harvest when compared with artificial fertiliser alone. Both of the trials used a 50% mixture of pelletised poultry manure and super. One crop had a yield close to average, the other was almost 50% higher than usual. A nearby crop grown on conventional fertiliser alone had many pods left behind after harvest.
Liquid fish is readily applied to soil by boom spray, injection into irrigation, or field jet in place of the boom spray. Foliar applications seem to work best at dilution rates of at least 50:1, and preferably 100:1 or higher. There is a wide variation in price and quality of fish emulsions. One of the most expensive we have used needed filtration prior to use, to remove what appeared to be scallop frill. It also smelled foul. The best we have used is the least expensive and has the most acceptable smell. Fish can be liquidised by a number of processes, heat, chemicals, or enzymes. The enzyme approach appears to produce the best end result, though all liquid fish fertilisers used have proved beneficial.
Application rates on pasture vary between 10 and 20 litres per hectare. Soil drenching at the rate of 60 litres per hectare for crops has given excellent results, though it appears that there has been very little, if any, work to determine optimum application rates at this time. Foliar applications of 10 litres per hectare to crops in place of urea appears to promote a high level of resistance to fungal disease and mites. Stock health is noticeably improved with less scouring due to parasitic worms.
Results from the use of liquid seaweed have been much more variable than with fish emulsion. This may be because of seasonal variation in the components of the kelp used in its manufacture. Dutch research shows spring harvested seaweed to be higher in auxins (plant growth hormones), autumn harvested is higher in abscissic acid. Abscissic acid is the hormone that stimulates leaf fall in deciduous trees and appears to confer pest and disease resistance. More work needs to be done in this area.
Like liquid fish, liquid seaweed can be manufactured by a variety of processes. Some products contain a certain amount of urea, the manufacturers claiming that it is necessary to stabilise the material. However, since some manufacturers do not use urea and their products are stable, this appears to be untrue. It is more likely that the urea is included to give a pronounced visual response. A crop of potatoes treated with liquid seaweed responded with a greater amount of foliage, but no measurable difference in the yield of tubers. An orchard trial at the rate of 9 litres per hectare promoted the growth of laterals in young apple trees.
Urea, Ammonium Nitrate and Ammonium Sulphate
There would appear to be little justification for the use of these materials for pasture production. Applications of water soluble nitrogen suppress the fixation of atmospheric nitrogen by clovers. Until the amount of fixed nitrogen is exceeded, there is no noticeable benefit and the cost is not only measurable in spending on fertiliser. The grass grown with water soluble nitrogen has more free amino acids and a higher water content. Some of the nitrogen taken up as nitrate is converted to nitrite in the sap of the pasture plants and this cause methaenoglobanaemia in the stock consuming it. This is a condition where an animal’s blood is unable to carry sufficient oxygen. High levels of nitrate in the soil suppress copper, resulting in steely wool, scours and parasitism (eg barbers pole worm).
As well, application of water soluble nitrogen in excess of the amount plants can use is either leached from the soil, or taken up by soil micro-organisms. In order to balance their diet, the micro-organisms consume organic matter in the soil. The result is that more and more water soluble nitrogenous fertiliser is needed to achieve the same result and soil structure deteriorates as organic matter levels decline.
Since the amount of nitrogen available to a crop from organic fertiliser is proportional to the amount of bacterial activity, a very poor season may very well justify the application of judicious amounts of artificial nitrogen. While it is clear that used alone these materials encourage fungal disease, aphids and acidify the soil, these negative effects may be ameliorated to some extent when used in conjunction with organic fertilisers. While the cost per unit of artificial nitrogen is much less than organic, the additional cost of pesticides, fungicides, and tractor fuel (to overcome the reduced organic matter content of the soil) must be taken into account. These costs are not just the purchase price and application costs. Since markets are now demanding residue-free produce, some pest and disease control materials are becoming severely restricted.
Organic farmers are often particularly injudicious in their assessment of the most commonly used fertiliser. There is no substitute for super when bringing eucalypt bushland into farmland. On the other hand, there would appear to be little benefit from excessive, long-term use. The main problem is that the bulk of applied superphosphate becomes locked up by chemical reaction in the soil.
The micro-organisms responsible for liberating phosphorus from the soil, making it available to crops, are suppressed by high levels of water-soluble phosphorus. Continual applications of superphosphate (or ammonium phosphate) keep these organisms inactive. Consequently, the farmer needs to apply all the phosphorus needs of the crop.
When a farmer stops applying superphosphate, there is usually a lag of 2-4 years during which the phosphorus liberating micro-organisms re-establish. This process is accelerated by applying proteinaceous fertilisers, such as animal manures and fish emulsion. The degree of recovery is dependent on the amount of locked-up phosphorus in the soil. Nearly always, pasture production returns to what it was prior to stopping. Heavy feeding crops often need more phosphorus than the soil biology can supply to produce the yields that are decreed necessary to remain economically viable. There appear to be three ways out of this double bind. The first would be to apply small amounts of super alongside organic fertiliser. The second, and probably better approach, would be to apply phosphorus as a foliar. This would allow better control of the amount applied and the soil micro-organisms would not be affected. The last would be to include reactive phosphate rock in the composting process used to manufacture pelletised poultry manure, or in vermicomposting with manure earthworms.
Where there is a demonstrable deficiency of phosphorus, rock phosphate offers several advantages over superphosphate. It is less expensive, contains a higher percentage of phosphorus, does not inhibit the soil micro-organism that liberate phosphorus and it doesn’t acidify the soil. The reason it has not been more widely used in the past is it is not water-soluble. On this basis, conventional agricultural theory said it could not possibly work. In more recent times, this attitude has been modified to “it works, but only in acid soils”. Organic farmers have known for years that it also works in biologically active soil. Trace elements are removed in the acidification process of super manufacture. Reactive phosphate rock, being unacidified, retains any trace elements in the original material.
There are only a few potassium fertilisers available in Australia. The most common is muriate of potash (potassium chloride) which is mined from natural deposits in Germany. Many plants are sensitive to excessive chloride and overuse of muriate of potash on crops, particularly potatoes, has led to levels that are cause for concern.
Sulphate of potash (potassium sulphate) is much preferred. Unfortunately, this material is manufactured from muriate by chemical reaction with sulphuric acid, and so it costs significantly more. In some districts, kiln dust, a by-product of cement manufacture, is available and contains significant amounts of potash. While seaweed contains significant amounts of potassium, it has been used to manufacture potassium oxide by burning, it is generally far too expensive to be used for its potassium content alone.
Lime is said to not be a fertiliser by conventional agronomists. Its use is merely to reduce soil acidity. From the foregoing it should be apparent that the two major constituents of lime, calcium and magnesium, have much more important roles than this gross oversimplification would allow. The relative proportions of calcium and magnesium in the soil should dictate the type and quantity of lime used, rather than adjusting pH using the cheapest source of lime regardless of its analysis. This latter approach often leads to a severe imbalance.
When the imbalance is a serious deficiency of magnesium relative to calcium, then the usual source of magnesium, dolomite, cannot be used. While there are sources of magnesium without calcium, they are relatively expensive. They include Epsom salts, Kieserite, magnesite and magnesium oxide. All of these sources are acceptable from the point of view of improving soil fertility, the same cannot be said regarding price. The least expensive is magnesium oxide, followed by magnesite. The most expensive is Epsom salts, followed by Kieserite.
While dolomite is relatively more expensive than ordinary limestone (it’s harder and more expensive to crush), it is cheaper than allowing the soil to become so magnesium deficient that straight magnesium materials become necessary.
Bio Dynamic farming places great store in what is known as BD500, or “horn manure”. This material is manufactured from cow manure placed in cow horns and buried over the winter months. The resultant material is black colloidal humus, rather than the green, smelly original manure. Between 25 and 35 gm is stirred rhythmically in 13.5 litres of lukewarm water for an hour. This liquid is then sprayed onto the paddock in the evening, the amount being sufficient for one acre. The BD500 is claimed to enhance the soil digestion process. That is, the raw organic matter in the soil is converted to humus and many BD proponents claim that fertility elements that are absent or deficient are created from existing elements in the soil.
While this sounds like the “muck and mystery” that organics has been labelled with for decades, there is no doubt that Bio Dynamic practitioners achieve remarkable results. Dr Doug Small of the Victorian Department of Agriculture and Rural Affairs has compared conventional and Bio Dynamic dairy farms and provided much food for thought. The Bio Dynamic practitioners, for instance, needed dramatically less irrigation than their conventional counterparts.
The foregoing preamble was not so much to spark interest in Bio Dynamic practices, but more an introduction to the proliferation of various materials that purport to achieve the same results. Unlike BD500, which costs between $1 and $3 per acre (ignoring the cost of stirring), these other soil activators cost significantly more. There is little doubt that many are no more than “snake oil”, but some have proved worthwhile. One such soil activator the author trialed, with rather a lot of scepticism, produced yield increases of between 15 and 50%.
Curiously, this material was being applied at the same rate as the amino acid betaine in trials conducted by the Tasmanian Department of Primary Industry. When the manufacturer of the soil activator was asked to comment on the similarity of results and application rates, he became extremely defensive. I imagine this was because betaine, a cheap by-product of beet sugar production, is much less expensive than the material he was manufacturing and I became somewhat sceptical of his explanations about his products.
Betaine, incidentally, confers some frost resistance to crops. Bill Hinchcliffe, head of the Riverina Ricegrowers Co-operative, says that organic rice is less susceptible to frost. Trials of several strains of grass with varying levels of cold tolerance revealed that the more tolerant strains had a higher betaine content. Perhaps organic growing methods increase the betaine content of crops and this in turn may also explain why many organic food aficionados perceive better flavour than in conventionally grown produce.
Apart from carefully trialing these materials yourself, there is no way to tell in advance if they will work. The author submitted several materials for comparative trials to the Tasmanian Department of Primary Industry. I was asked what my attitude to a negative outcome would be and I said that the results should still be published. The manufacturers of some products being trialed wanted any negative results suppressed.
Building Soil Fertility
Soil fertility can either decrease, remain constant, or be increased. The humus level, or Cation Exchange Capacity of the soil are the best indicators to use. The quickest way to decrease soil fertility is to use only water soluble fertilisers and to till the soil too often, especially when it is too wet. Soil fertility is conserved with minimum tillage, using water-soluble fertilisers only when strictly necessary, and by including green manure crops in a diverse crop rotation. Soil fertility can be increased by balancing the major nutrients, calcium, magnesium, potassium and sodium as described earlier, and by including a pasture phase in the crop rotation.
A cow generates 20% more manure than is required to grow the food she needs. Consequently, pasture accumulates fertility that can be converted to a cash crop for export without decreasing the net fertility of the farm. One Tasmanian dairy farmer admitted to the author that his best paddocks had been sown down by his father with a horse-drawn plough and never fertilised as there was no response to fertiliser strips.
Organic farmers use rotation of pasture with crops as an economic alternative to importing fertiliser. The relative lengths of the pasture and cropping phases are determined by the capacity of the soil to accumulate fertility and the particular crops that the farmer grows. The 100 kg/ha of nitrogen fixed by a sward of white clover is a sufficient amount to grow a worthwhile crop. Lucerne fixes even more nitrogen and can be applied as chaff to be harrowed in for a nitrogen boost to a crop. Lucerne also contains growth hormones that give increased yields beyond the result expected from its nitrogen content alone.
When a paddock is ploughed under for cropping, it is important to plough shallow. Organic matter buried too deep is decomposed by mainly anaerobic bacteria, so the process is fermentation, rather than humification. For optimum results, the organic matter should also be completely decomposed before sowing the crop. Many plants, particularly those we call weeds, contain growth inhibitors (phyto-toxins) and until they have decomposed, they will inhibit seed germination and reduce the vigour of the crop.
The bacteria responsible for humification need the right working conditions to perform to the best of their not inconsiderable abilities. The most important of these conditions are warmth (10-20°C), air and moisture. Of secondary importance, but still vital for best results, is a source of protein. Quite small inputs of protein can produce results seemingly out of all proportion to the amount applied. While solid fertilisers, such as pelletised poultry manure, are cheap to buy, the convenience of fish emulsion applied by boom spray or field jet can give a more economic result. The soil activators that are touted as “essential” have already been discussed above.
Tillage of the ploughed paddock should be the absolute minimum required for weed control. Each time the soil is tilled, the organic matter is reduced by oxidisation. The humus is converted to nitrate (among other substances) and in the absence of a crop, this nitrogen can be lost through leaching. Tillage also reduces earthworm numbers, damages the crumb structure and the diversity of microorganisms decreases.
A green manure is a crop grown specifically for fertility enhancement. Quite often, green manure is confused with cover cropping. The latter is specifically grown for weed suppression and prevention of soil erosion when the ground would otherwise remain bare for a period of three months, or more. Of course, a crop can be grown for both purposes, but the type of crop grown is determined by the most important purpose.
European organic farmers have brought green manuring to a state approaching perfection. They almost invariably sow a mixture of a legume, a cereal and a crucifer. The legume fixes nitrogen. The cereal straw produces soil binding materials when it decomposes, called mucins. They bind the soil in the crumb structure that is essential for good drainage, aeration and ease of tillage. The sulphur compounds in the crucifers are believed to enhance the health of the soil.
Typical legumes include lupins, tick beans, field peas and tares (vetch). Typical cereals include oats, rye and barley. Typical crucifers include oilseed radish, rape and mustard.
The optimum time to plough a green manure under is when the flowers are just starting to form. At this point, the protein content is at a peak. Afterward, the fibre content increases, necessitating the application of additional protein, or a longer wait for complete decomposition. The effectiveness of a green manure is enhanced when the carbon to nitrogen ratio is between 25 and 35 to 1. That is, the protein content complements the fibre. Looked at from the point of view of using pelletised poultry manure, its effects too are greatly enhanced when used in conjunction with a fibrous green manure due to the low fibre content of the poultry manure. The remarks above applying to ploughing in pasture also apply to green manures. Wilting the green manure by rolling or mowing prior to turning under promotes an increase in decomposition rate.
Cover cropping requirements are rapid establishment to get ahead of the weeds, and for plenty of fibrous roots that will hold the soil together. Usually this is a cereal, or annual ryegrass. One suspects that a mixture of species would perform better from the point of view of the soil biology vastly preferring a mixed diet, but this may not be as economic as using a single species.
Organic fertilisers are generally considered to be more expensive than artificial fertilisers. On the face of it, this is true. In Tasmania in 1994, a tonne of Dynamic Lifter cost approximately $400; the equivalent nutrients as artificial fertiliser cost approximately $170 per tonne.14 In reality, the Dynamic Lifter was better value for money on several counts. According to the Soil Handbook that comes with the La Motte soil testing kit, the following table of nutrient use obtains:
Percentage obtained by crop in one season
Artificial fertiliser seems to be ahead, but there is a marked difference over several years. The artificial fertiliser needs to be applied at the same rate, year after year. While 30% of phosphorus in artificial fertiliser is used by the crop during a season, 40% of it is chemically locked up, or lost through erosion, contaminating groundwater and streams. The 70% balance of the phosphorus in the animal manure remains for use by the subsequent season’s crop. The first year of applying Dynamic Lifter would cost $400 versus $170 for the artificial fertiliser. Subsequent applications of Dynamic Lifter to maintain the equivalent input of nutrient would cost only $120. After ten years, the total cost of artificial fertiliser is $1700; the equivalent Dynamic Lifter would have cost $1480.
But this is not the whole story. Dynamic Lifter stimulates the proliferation of bacteria and other micro-organisms that render the locked-up phosphorus available for use by plants. On a paddock with a long history of superphosphate use, these reserves of phosphorus are quite significant. Build-up of the necessary organisms to fully exploit “unavailable” phosphorus generally takes three to four years. The farmer then has the choice of increasing yield, or reducing fertiliser input to maintain the same yield.
Eyeless, legless, faceless, earless, voiceless, the earthworm is not much to look at — a mere squirming piece of flesh. Yet with its powerful muscles, its two stomachs… its false teeth, it is able to carry out remarkable works” — John Stewart Collis
While some aspects of plant nutrition were partially covered in the preceding chapter, it is a complex area beyond the scope of this small book to cover thoroughly. However, it is the author’s belief that some understanding of the underlying principles will enable the improvement of farming beyond that currently considered acceptable.
The classical model of plant nutrition has it that nutrients must be in water solution to be taken up by plant roots. To be absorbable, the molecules must be small. To be water soluble they must be simple salts. All of our current standard mineral fertilisers fit this description. The model further states that these nutrients are taken up in the water from the soil as a result of transpiration of moisture through the plant leaves. While hydroponics is the epitome of this model, when we take a closer look, things start to look distinctly dodgy.
The model implies that for growth to take place there must be transpiration of moisture through the plant leaves to create the flow of nutrient-bearing water. In a terrarium, the atmosphere is saturated with water (100% humidity), so transpiration is almost non-existent, yet plant growth clearly occurs. It would be hard to find growth rates to equal those of steamy tropical jungles, where humidity is high and therefore transpiration rates are low. Conversely, a high transpiration rate should result in faster growth. My observation is that windy conditions and low humidity result in poorer growth.
Let’s look at the soil. A conventional farm soil supporting good plant growth exhibits the high electrical conductivity associated with plenty of ions15 in solution. On the other hand, a good organic farm soil supporting similar growth shows a very low electrical conductivity, indicating that there are minimal numbers of ions in solution. Part of the answer to this conundrum is that the organic farm soil contains more humus which, like clay, has negative electrical charges to hold the positively charged ions out of water solution.
Both humus and clay have surfaces covered in negative electrical charges. Since negative electrical charges attract positive electrical charges16 these surfaces are covered with positively charged ions (cations). These cations include calcium, magnesium, potassium, sodium, copper, cobalt, ammonium, iron, aluminium and hydrogen.
When a plant needs cations, its root hairs emit hydrogen ions. The hydrogen ions displace the cations from the clay, or humus colloids and the cations are then taken up by the plant root hairs. It should be obvious that if the ratio between the cationic nutrients held by the soil colloids is unbalanced, then the nutrition of the plants will also be unbalanced. The plants will be unhealthy.
If all, or nearly all of the plant returns to the soil, as in a forest, the pH will remain pretty constant over time. Where the cationic nutrients are removed in crops, the soil will tend to gradually become more acidic and less fertile unless they are replaced. While our shallow rooted crops exploit very little of the soil profile, deep rooted plants can exploit mineral reserves out of their reach. When the residues of these plants decompose, these minerals are released for use by the shallow rooted crops. Where this occurs to a sufficient degree, the process of acidification can become so slow as to be imperceptible.
The cations required in the greatest quantities are calcium and magnesium, which is why we generally use limestone to correct an acid soil condition. Unfortunately, it is a rare limestone that has the appropriate balance between calcium and magnesium. Unless the ratio between calcium and magnesium in the soil is known, the appropriate liming materials and quantities will also be unknown.
The level to which the Cation Exchange Capacity of the soil is filled is called the Base Saturation and is expressed as a percentage. The higher the humus level, the higher the Cation Exchange Capacity, Base Saturation and consequent capacity of the soil to produce. Since clay also contributes to the cation exchange capacity, soils with more clay and/or humus require much greater amounts of calcium and magnesium to produce a given pH change than a sandy soil, or one low in humus. Cation Exchange Capacities of up to 28 meq% have been recorded in New Zealand. My own very productive market garden soil has a CEC of 20 meq% and good pasture levels are around 10 meq%.
Then there are the negatively charged nutrients, nitrate, phosphate, sulphate and so on. Clearly they are not part of the plant root/colloid interchange. Dr Allan Smith of the CSIRO has written about the interaction between soil micro-organisms, oxygen and ethylene in the soil. At some risk of misrepresenting Dr Smith’s work, we will attempt a very simplified explanation.
Soils with good aeration are more fertile than those with poor atmospheric gas exchange. There is more oxygen available to the micro-organisms that require it and many of them are implicated in the release of nutrients from the soil. However, even in a well aerated soil there are pockets of low oxygen level. These pockets allow the proliferation of anaerobic bacteria that are suppressed by high oxygen levels. The anaerobic bacteria generate ethylene gas, the gas that ripens fruit. In the soil, ethylene suppresses the aerobic bacteria, decreasing their rate of reproduction at lower levels and putting them into suspended animation at higher levels. When this happens, the aerobes use less oxygen, so the overall level of oxygen in the soil increases. Oxygen has the same effect on the anaerobes as ethylene does on the aerobes, so there is a balancing effect. Neither the aerobes, nor the anaerobes can predominate.
This situation only obtains in a soil that has a continuous source of fresh organic matter for the anaerobes to convert to ethylene. Soil that is tilled too much and becomes over-rich in oxygen disrupts the production of ethylene. We will look more closely at the effect of soil compaction and the overabundance of anaerobic bacteria in the next chapter. Excessive levels of nitrate also disrupt the oxygen/ethylene cycle. This is because the production of ethylene is dependent on the availability of iron and the bacteria that render iron available are suppressed by nitrates. Applying ammonia instead of nitrate is not a solution, since nitrifying bacteria convert ammonia to nitrate.
At the same time iron is released from its chemical bondage by bacteria, so too are the rest of the iron compounds, phosphate and sulphate etc. The now soluble negatively charged phosphate and sulphate become available for absorption into the plant. The iron is adsorbed onto the clay and humus particles after catalysing the production of ethylene. Many plants do not absorb phosphate directly, but do it via an intermediary. Fungi that live on the plant roots, called mycorrhizae, consume the phosphate and then trade the phosphate with the plant root in return for carbohydrates.
This is not the whole story, however. Earthworms are also responsible for the liberation of phosphate and calcium (among other elements) from the silt particles they ingest. Animal manure, dropped on the soil surface by grazing animals, has much of its nitrogen in the form of ammonium carbonate. Fresh manure tilled into the soil has its nitrogen converted to nitrate by the nitrifying bacteria. In effect, it is little different to applying nitrate from the bag. Left on the surface, it is consumed from underneath by manure worms. These little creatures resemble the soil-ingesting pasture earthworm, but are much more active when disturbed. One common variety is called the red wriggler. The nitrogen in the manure they consume is converted to protein.
All of these biological mechanisms require continuous inputs of fresh organic matter — carbohydrates and proteins. Inputs of nitrate and water-soluble phosphate disrupt them. Excessive tillage of the soil produces excessive aeration which in turn allows the organic matter to be consumed at an extravagant rate. When most of the organic matter has been consumed, the soil structure collapses leading to very low levels of aeration and the proliferation of anaerobic bacteria. Excessive tillage, elevated nitrate levels and muriate of potash also reduce earthworm numbers.
From the foregoing it should be apparent that what is required for good biological activity in the soil is the steady, frequent input of small amounts of organic matter and minimal tillage. This leads to optimum use of nutrients in the soil by the crop.
In promoting soil biological activity where the soil is badly out of balance, it would appear to make more sense to apply any shortfall of major nutrients as foliar sprays, rather than disrupt the soil biological cycles further.
Soil Analysis — A hit and myth affair.
Nutrient analysis of soil has become very popular in recent decades. As a guide to fertiliser use, it can be misleading and frustrating — or a useful aid to profitable farming.
The problem is that most analyses rely on the use of a weak acid to dissolve the nutrients out of the soil in order to measure them. The assumption behind this is that plants can only take up fertility elements that are readily soluble in water. While the results from soil analysis are useful in prescribing the amounts of conventional amendments required to grow a crop in the average farm soil, they fall well short when organic fertilisers are used, or when land that has been under pasture for several years is brought into cropping. They are even less useful when the soil has been under an organic regime for any length of time.
A field officer for a vegetable processor told me that he came across a perfect example of this. One paddock that tested as ideal for a crop of peas ended up not being harvested because of the poor crop. Another that tested as mediocre grew the record crop for the season. The differing organic matter levels in the two paddocks explains the apparent incongruity.
The two most difficult to assess major elements are phosphorus and nitrogen. Organic fertilisers and the organisms they feed release phosphorus from the soil not detected by ordinary soil analysis. Much of the nitrogen in a good organic soil is in the form of protein, and the nitrate and ammonium tests for soil nitrogen levels underestimate this important source of nitrogen. Crude estimates based on soil carbon can be used, but the soil carbon level is determined by igniting the carbon and measuring the weight loss. It is not an accurate estimate of the soil’s protein content.
This does not mean that soil analysis is bereft of utility. We have already referred to the importance of the ratios between calcium, potassium, magnesium, sodium, trace elements and hydrogen ions. The better soil testing laboratories include the percentage cation figures in their analyses, though only for calcium, magnesium, potassium and sodium. The reason for this is that most of the trace cations are expensive to test for. Bringing the ratios of the major cations into the desired range without soil testing is not feasible. When the soil is amended to do so, the consequence is an improvement in crop and stock health. The degree of change is dependent on how far out of balance the soil was prior to amendment.
Soil testing for trace elements is not only expensive, there is little relationship between soil levels and the amount taken up by crops. Again, humus appears to play a role in this, but there is also the issue of interaction between elements.
The diagram on the previous page shows some of the known relationships between elements. This chart shows the effect of various plant nutrients on each other. The solid lines show that one element suppresses another in the direction of the arrow head. For some pairs of elements, both are suppressed when excessive amounts occur. Similarly, the dotted lines show stimulation.
For example, even heavy applications of zinc will not “cure” zinc deficiency if there is an excessive level of calcium. In such a circumstance, there would also be symptoms of phosphorus, magnesium, manganese, potash, boron and iron deficiency.
The soil test results below are from the author’s property and a neighbouring property. The soil type is silty clay, approximately 50% clay and 50% silt; the sand content is less than 5%. Annual rainfall is averages 800 mm. All three sampling sites were within 100 metres of each other. Pasture A is the neighbour’s property and is under a conventional fertiliser regime. Pasture B is my hay paddock. At the time of testing, the paddock had received no fertiliser inputs for twelve years. Despite this, and seven hay cuts that were mostly sold off, the last hay cut was approximately 300 bales per acre which is considered an excellent yield in the district. The market garden block initially received dolomite lime to lift the pH from 5.5 to 6.5 (2.5 tonnes/ha) and muriate of potash (200 kg/ha) as determined by soil test to overcome potassium deficiency. Over the ensuing ten years, only compost has been applied. The crop rotation in the market garden is four crops every three years. Both areas received applications of Bio Dynamic preparation 500 at the rate of 35 gm/acre in 1988 and 1989.
There are several interesting things to note in these soil test results. Despite applications of super every year or so, Pasture A has less available phosphorus than Pasture B which has had no fertiliser inputs for over a decade. Pasture A has a higher organic carbon level than Pasture B, but its lower Cation Exchange Capacity, indicates that less of the organic matter is in the form of humus. Both paddocks have good earthworm activity. Both paddocks also show very low magnesium relative to calcium and this reflects in less than optimum stock health. The claim by some Bio Dynamics proponents that Preparation 500 alone can improve this situation is not borne out by the soil test. However, the topsoil depth in Pasture B increased markedly (from 75 mm to 250 mm) in the two year period following application of Preparation 500.
The market garden area, despite having more than twice the lime content of either Pasture A, or Pasture B, has the same pH. This is because the much higher Organic Carbon level, mostly humus, is buffering the pH. The disparity in lime levels illustrates the folly of liming the soil to change pH while ignoring the contribution of humus.
The Cation Exchange Capacity, expressed here in meq% (percentage milliequivalents), is a measure of the soil’s fertility. That is, it’s a measure of the crop yield that the soil is capable of. We have seen the CEC of the major vegetable producing soils from the NW and NE coasts of Tasmania vary between 10 and 20, most toward the lower end of the range. In New Zealand, CECs of up to 28 have been measured and the best European and United States soils are said to be even higher.
* Estimated as being the same as Paddock B now since no fertiliser has been added. The estimate ignores what was exported in the 7 hay crops.
The extraordinary level of phosphorus in the Market Garden sample cannot be explained solely on the basis of the phosphorus content of the applied compost. The soil test indicates that there is now nearly 1.4 tonnes/ha more phosphorus (equivalent to approximately 14 tonnes of superphosphate) than the amount detected in the original soil plus that applied. Also appearing in significant amounts are calcium and magnesium, equivalent to about 5 tonnes/ha more dolomite lime than was applied. Since phosphorus, calcium and magnesium were also being exported in the crops sold, the disparity is even more remarkable. The only rational conclusion to draw is that the increased biological activity associated with the addition of compost has released substantial amounts of phosphorus, calcium and magnesium not detected by the original soil test.
The low nitrate levels in Pasture A and Pasture B would probably lead to conventional agronomists advising applications of urea, or ammonium nitrate. However, neither paddock shows the slightest sign of nitrogen deficiency. In both paddocks there is more than adequate nitrogen, in the form of protein. These low nitrate figures indicate that very little leaching of nitrogen can occur. The higher nitrate level in the Market Garden sample is probably due to the fact that it had recently been tilled following a harvest of beetroot. Tillage oxidises humus, releasing nitrogen in the form of nitrate.
All three samples show magnesium needs to be increased relative to calcium. While the Market Garden sample indicates that dolomite limestone has ameliorated the situation, a source of magnesium without calcium would have achieved a better result. Epsom salts (magnesium sulphate) would be the best source as it would improve the low sulphur levels (not shown). Unfortunately, it is too expensive. Magnesite, or magnesium oxide would be more economical.
The high potassium level in the market garden indicates that the original application of potash was a complete waste of money. Had I waited for the increased biological activity to make the potassium available, I could have eliminated the expense. Ah! The wisdom of hindsight.
Pests and Diseases
Insects and diseases are the symptoms of a failing crop, not the cause of it” — William Albrecht
If the approach taken by most agricultural scientists and books written by them were a guide, then pests and diseases are the result of a deficiency of pesticides and fungicides. Of course this is not so. Pests and diseases are almost always the result of plant stress. These stresses include:
- nutritional deficiency
- water shortage or excess
- extremes of temperature
- chemical damage
Not a direct stress, but also important, is the decimation of predators caused by pesticide use.
All of these factors are at least partially under the farmers’ control. If the stresses are avoided, or diminished, then many plant pests and diseases either simply do not occur, or fall below levels that justify control. The question then arises of the economic viability of avoiding plant stress versus using pesticides and fungicides. All of the stresses listed above decrease crop yields, not just through crop loss caused by the pests and diseases they encourage, but more directly.
Let’s take spider mites as an example. You will probably have noticed that they are much worse in periods of hot, dry weather. Plants under stress from water deficiency are what spider mites demand. Of course a plant that is suffering from water deficiency is also not going to yield as well as it would were it supplied with adequate levels of water. Is it more economical to allow crops to suffer water deficiency, reducing yields and use miticide, or to supply more water, increasing yields and eliminating the cost of the miticide?
One way to supply more water without the necessity of additional irrigation or rainfall is to improve the water-holding capacity of the soil and also the infiltration rate of water falling onto it. Increasing the humus level will accomplish this. Humus is important in utilising water to its utmost. Water that runs off is not just wasted, but also carries topsoil and nutrients away from the crop.
Another common pest, one that is almost ubiquitous, is the aphid. These little suckers probably cause more damage than any other insect. The first thing to consider is their nutritional needs. Aphids cannot digest complete protein; they require free amino acids (the building blocks of protein). Excessive amounts of water-soluble nitrogenous fertiliser creates the condition of high levels of free amino acids in plant sap, effectively a dinner invitation to aphids. Conversely, feeding protein to plants reduces the level of free amino acids and minimises the attractiveness of plants to aphids.
Many insect problems are caused by monoculture, that is the growing of vast areas of a single crop. In a polyculture, such as a natural ecosystem, insects have the problem of finding the next plant to feed on. Not only is it likely to be some distance away, its odour, essential for insects to find it, is masked by the odours of all the other plants in the insect’s vicinity. Not only that, some of those other plants harbour predators on the insect, so it is more likely to be consumed in a polyculture than in a monoculture.
Insecticides, natural or synthetic, are a poor answer to the problem of excessive insect pests. This is because insect predators necessarily reproduce more slowly than their prey. If it were otherwise, then they would eat themselves into starvation. Most insecticides kill pest and predator alike, so unless they are used continuously, they give pests an edge over predators. Unfortunately, continuous use is not just expensive, it leads to pesticide resistance. Then, when a pest outbreak occurs, there is one less insecticide in the arsenal.
Some predatory insects can be encouraged by providing attractive food sources. For instance, hoverflies whose larvae consume aphids are attracted to flowering umbelliferous plants whose nectar they consume. Traditionally, Britain’s hedgerows provided habitat for many predators on insects. It is no coincidence that the decline of hedgerows in Britain has been accompanied by dramatically increasing pest problems. Many Australian farmers have discovered the virtues of leaving some bush to provide a predator reservoir, or reintroducing bush to their farms where similar problems are occurring.
Many birds are avid consumers of insects and insect larvae. In the New England Tableland, there has been an interesting study of a species of bird that consumes grass grubs. It is the female that consumes the grubs, while her male counterpart consumes the nectar of flowering gums. The females will not feed more than 150 metres or so from the males, so the maximum distance of pasture from trees needs to be no more than this distance for natural grub control. Growing belts of trees and shrubs on farms has other benefits apart from pest control. They keep groundwater under control and reduce evaporation of rainfall by reducing wind speed. Stock chilled by wind have to consume more feed to keep warm, so windbreaks can provide increased productivity. The shade from hot summer sun they provide reduces heat stress.
Insects that appear to be pests at first glance can also be seen in a quite different light. Japanese agricultural researcher, Masonabu Fukuoka, was trialing a pesticide to control a stem borer that afflicts rice. Much to his surprise, the first trial showed a yield decrease in the paddy treated to control the stem borer. A repeat trial also showed that killing the pest decreased rice yield. He came to the conclusion that plant density was the issue. The stem borer thinned the rice plants to produce a higher yield than when they were too crowded. The funds for this research came from a pesticide manufacturer who forbade publication of this interesting result. After all, it would have reduced sales of their products! Fukuoka, having drawn a number of conclusions from his years of agricultural research, took up organic farming and put his ideas into practise.
When we look at a natural ecosystem, which by definition is devoid of pesticide and fungicide inputs, we see very little pestilence and disease. Note that there is not a complete absence, just a very low background level. Of course, such a system is not very productive from the human economic viewpoint, which is why we developed farming. What organic farmers are attempting to do is bring the control mechanisms in the natural system into our more productive farming systems. The problem here is that the more we improve productivity, the further removed from the natural ecosystem we get. Maintaining the mechanisms of the natural ecosystem alongside improved productivity requires considerable effort and expertise.
Paradoxically, peasant populations the world over have achieved this, yet we have been trained to perceive peasants as ignorant. Miguel Altieri, who coined the term agroecology, took a group of botanists and a group of peasants into a Central American forest. Each group was required to identify as many different plants as they could. The peasants won by a country mile. In the UK, there was an archaeological experiment carried out at a place called Little Butser. The idea was to equip students only with the resources available to Britons of the Bronze Age and observe the way they lived. Some of the outcomes were quite remarkable and certainly unexpected. The Little Butser Bronze Age village produced 15 times more food than historians estimated such a village could produce at the time. This implies that either the population was 15 times greater than previously believed, or that excess food was exported.
We knew from archaeological digs that wheat was stored in pits dug in the chalk subsoil, capped with clay. The experiment revealed that carbon dioxide generated by the wheat killed any insects that would have consumed the stored grain. The wheat varieties chosen for the experiment were those known to have been grown in that period. They were much higher in protein than modern varieties and one turned out to be unpalatable to rabbits. Today’s wheat farmers have an ongoing battle with rabbits and I wonder if there has been any research into breeding a less rabbit-susceptible modern wheat variety.
What we are trying to do here is establish, not that imitating peasant practises is the way to go, but that there are important lessons to be learned from them. World food production increases are slowing down; conventional agriculture has gone just about as far as it can. We must either improve the technology of food production, or decrease population growth. Since the latter is outside the scope of this book, we are concentrating on the former. We also believe that there are many other reasons for improving our farming.
We referred in the previous chapter to the oxygen/ethylene cycle and its effects on soil biology. It is a feedback mechanism for maintaining the balance between aerobic and anaerobic microorganisms. Its existence was discovered in natural ecosystems and appears to be what the best organic practises can achieve.
Ethylene is a gas produced by ripening fruit and decomposing vegetables. When we wrap tomatoes to ripen them, we are capturing the ethylene and preventing its escape, thus accelerating the ripening process. Ripe bananas are prolific producers of ethylene, so this is why we put a banana in a bag with tomatoes to accelerate their ripening.
Disease organisms are organisms that decompose organic matter and can be looked at from two differing viewpoints. When they are attacking our living food crops they are a problem. When they are decomposing crop residues, they are converting them into food for the next generation of plants. What is it about our current agricultural practises that allows what are usually benign organisms to run out of control? What keeps them in check under natural conditions and in organic farming? Let’s look at what happens to organic matter under the systems of organic and conventional production.
Plants consist of mainly carbohydrate (starches, sugars, cellulose) and proteins. When plant matter is incorporated in the soil, it is decomposed by the soil microorganisms. In the presence of oxygen, the carbohydrates are decomposed by fungi to generate carbon dioxide and water. The carbon dioxide displaces oxygen. These fungi are just as happy without oxygen, but now decompose the carbohydrate to alcohol and carbon dioxide. Under this condition, anaerobic bacteria come into the picture and decompose the carbohydrate to methane and ethylene. The ethylene suppresses the aerobic bacteria so they consume less oxygen. Consequently, oxygen levels increase, suppressing the anaerobic bacteria and the ethylene level then decreases. This allows the aerobic bacteria to revive and they transform the alcohol to acetic acid which dissolves nutrients from the silt. Proteins are decomposed to generate the free amino acids they require and some is converted to ammonia. Other aerobic bacteria convert ammonia to nitrate which is absorbed by plant roots. In the process these aerobic bacteria also convert oxygen to carbon dioxide. Plants convert carbon dioxide and water to carbohydrate, liberating oxygen. The plants then die to begin the cycle once more.
This is a grossly simplified view of what happens; there are over 2,000 different species of interacting micro-organisms in a healthy soil. However, it is enough to give us some insight into what we can do to ensure these process occur and what happens when our farming practises interfere to create undesirable consequences. It illustrates the principle of the dynamics of a functioning ecosystem. Each micro-organism has a different purpose and also provides the checks and balances to maintain the system. As farmers, we must either provide conditions that allow these processes to occur, or accept the consequences of hindering them.
What we call disease organisms are part of this ecosystem. They only become a problem when they are allowed to predominate over organisms that in a natural ecosystem keep them in check. Our farming practises, tillage, fertilisers, pesticides, herbicides and fungicides, all affect the system. Nitrate fertilisers suppress ethylene production, the feedback mechanism for keeping fungal “diseases” in check. Many fungicides kill bacteria, and as we have seen, bacteria are an essential part of the soil ecosystem. The speed of gas diffusion is a function of soil structure. Insufficient air in the soil is a stimulant to the anaerobic organisms and suppressant of the aerobes. Excessive aeration leads to the rapid depletion of organic matter, the food source of microorganisms. Herbicides are implicated in the chemical lock-up of trace elements needed by plants and micro-organisms for the formation of essential enzymes.
Does this mean we are advocating the immediate cessation of all synthetic inputs? Not at all! The establishment of a healthy soil ecosystem requires time and effort, which is a cost. The consequent reduced need for the supposedly necessary external inputs is a cost reduction. The difference between the two may be a profit, or a loss. For ecologically acceptable farming to be viable, a profit is essential. For a fortunate few farmers, the profit need not be monetary, but a sense of well-being engendered by not using toxic, or potentially toxic chemicals. The majority of farmers caught in the financial squeeze between high input costs and low returns must trial these techniques carefully to assess their economic viability.
A further factor is the changes in external economic conditions. The origin of our current farm economy woes was the demand for abundant and cheap food. Having succeeded in supplying that demand, we now find that requirements are changing. The consumer is expecting abundant cheap food without the chemical inputs. It has not yet occurred to them that they could be requiring a decrease in the standard of living for farmers in order to maintain their own. We need to inform them of these and other issues vital to the well-being of farming and bring them into the decision-making process. In some European countries, where the negative impact of farm chemicals is more pressing, governments are subsidising the farm conversion process, or requiring the cost of damage caused by agricultural chemicals be included in the purchase price.
Another factor to take into account is the small, but growing number of consumers who are aware of the problems of agriculture and many of them are sympathetic to farmers’ needs. They have shown a willingness to pay significant premiums for organically grown produce. Ian McLaughlin, when he was shadow minister for primary industry, called for cooperation between farmers and the public in solving farmland degradation. Revegetation in the form of trees on farms is a cost most farmers can’t meet unaided. McLaughlin’s suggestion is that farmers donate the 10-15% of the farm that need to be in trees and the public provide the trees and labour. The farmer benefits from improved productivity and reduced land degradation. The public benefits in improved landscape, water quality and reduced costs of production.
In any event, while a wholesale overnight change is impossible, small incremental changes are not only possible, but highly desirable. What works well on one farm does not necessarily work well on another. What may have a negative impact on profit in one location may have a positive impact at another. By proceeding slowly and sharing our experiences, we can expect to develop agricultural systems that are better and more organic than those predominating now, but they will not necessarily be identical to what we currently call organic. It would be a foolish person indeed who declared that current organic farming practise is a panacea for all our agricultural problems. After all, as we discussed in the early part of this book, our pre-industrial agricultural practises were just as capable of massive land degradation as our currently much maligned conventional agriculture. It’s just a lot quicker with tractors than slaves. And it’s worth noting that nature, unassisted, takes geological ages to repair the damage we can cause. If we expect to continue supporting a large human population on planet earth, we have a lot of hard decisions to make over the next decade, or two.
While the mechanisms of pestilence and disease as we currently understand them appear complex, the solutions to them, generally speaking, are not. While we cannot create the diversity in farm ecosystems that occur in natural ones, any move to increase diversity will help. An example from the Lockyer Valley in Queensland will illustrate. Broccoli growers adopted a number of strategies to reduce their pesticide inputs. One was the growing of a row of canola every few metres among the broccoli. The canola harbours a predator on one of the target pests and coincidentally provided some wind shelter, since it is taller growing than the broccoli. Another strategy was not growing broccoli when the market was flooded and prices so low that it wasn’t really profitable to produce. This discontinuity created a feeding problem for the pests and reduced overall numbers. Dipel (Bacillus Thuringiensis) was adopted for some caterpillar control. This is a living organism, so it has the capacity to breed in the environment and infect subsequent generations of the target pest. Since the bacterial toxin is highly specific to caterpillars, only the target organism is killed. The last strategy was to rotate among a group of chemically unrelated pesticides to reduce the problems caused by target pests developing immunity to the spray, an invariable consequence of using a single pesticide continuously.
This illustrates a number of organic principles:
- Any increase in ecodiversity is likely to help reduce the problem
- There are incidental benefits to the adopted strategies other than the main goal
- Crop rotation provides pest control benefits
- There are biological alternatives to chemical pesticides
Specific Disease Control Methods
As has already been indicated, organic methods are rarely single-shot. Nearly always, a number of strategies are adopted. One of the simplest ways to reduce fungal disease on leaves is to ensure that adequate sunlight and air movement occur in a crop. Most fungi thrive where there is high humidity and shade. Soil fungi are more troublesome where there is inadequate humus in the soil and poor drainage.
Another strategy almost universally adopted by organic growers is varietal selection. The more cynical organic producers believe that many modern crop varieties are promoted because of their dependence on synthetic inputs. While older varieties yield less under a conventional regime, they can outperform modern varieties in an organic context without the expensive necessity for spraying.
Nearly all fungal diseases are controlled by the stimulation of bacterial activity. The bacteria appear to be competitors for the same ecological niches as fungi. Sclerotinia, botrytis, phytopthera, mildews and apple scab have all been controlled by applications of fish emulsion and a liquid extract made from compost. Increasing the pH of the leaf surface prevents spores of some fungal diseases from germinating. Examples of the use of this technique include control of botrytis and apple scab with applicationsof a 3% solution of sodium silicate or a saturated solution of calcium hydroxide (Limil).23 Also organically acceptable are most of the copper sprays, such as Bordeaux and Burgundy mixtures, sulphur, lime sulphur and sodium bicarbonate (baking soda). Where seed rotting is a problem, potassium permanganate (Chondy’s Crystals) is used as a seed dressing. Damping-off of seedlings is generally controlled by lightly dusting the soil surface with sifted wood ashes, or hydrated lime. Covering seeds with sand rather than seed raising mix also helps by improving drainage around the stem where the infection occurs. Mildews can be controlled with phosphorous acid.
Many diseases are a response to unbalanced plant nutrition. The emphasis on providing for the plants’ nutritional requirements mitigates against most fungal diseases being a problem for the organic grower.
Research is currently under way to develop biological controls for a number of pest and disease problems. While this is laudable for its potential to reduce the level of synthetic pesticide use, this research is of more use to the users of these chemicals than to farmers whose management precludes their necessity.
One aspect of organic production that is remarked upon with some frequency is the claim for longer shelf-life of organic produce. Opponents of organic production say that because organic produce is not protected with chemicals, it is more subject to bacterial and fungal contamination. Therefore, they say, organic produce is more hazardous to the health of the consumer than the chemical residues in conventionally grown produce. This is not borne out by scientific research.
Production Method and Storage Loss
Potatoes 24.5% 16.5%
Beetroot 59.8% 30.4%
Carrots 45.5% 34.5%
It is easy to see from results like these that yield could be lower in the paddock, but more produce be saleable at the all important market end of the production process.
Ted Sloane was an agricultural extension officer in New Zealand when he decided to take up farming. He decided to put his conventional agricultural training to practical use by growing kiwifruit. The results in terms of yield were extremely gratifying; they were the best in the district. Unfortunately, the keeping quality of the fruit was poor and losses in storage were over 20%. Consequently, his income was well below the district average.
It was fortuitous that one day when Ted was burying the recently deceased domestic cat that he noticed the prolific number of earthworms in the home garden in contrast to their complete absence in the orchard. It was then that Ted decided to replace his conventional fertiliser program with organic fertiliser. He chose a liquid fish product that was available locally. The earthworms proliferated and the wind-drifts of leaves that previously banked up against the windbreaks for many months were rapidly consumed by the improved soil biology. Ted managed to reduce his spray program from thirteen, or more per season down to two, or three. As a consequence of this, Ted went on to develop his own fish fertiliser and become a manufacturer. Despite solving the kiwifruit growing problem, he was unable to control the ever decreasing price he received for the fruit.
Dr Mike Walker of Watercress Valley Herbs trialed a range of fertiliser programs on parsley. Not only was the fully organic patch yielding better than the fully chemical, but the storage life of the organic was way ahead. From his customers’ point of view, it was more economical to purchase longer storing herbs at a higher price less frequently than to pay less and have to buy more frequently.
Specific Pest Control Methods
Here again the organic grower has a multiple strategy of defence. The first line is to create as ecologically diverse an environment as possible. The few remaining pest problems can then be controlled by relatively innocuous materials. Aphids are controlled by soft soap (potassium stearate, Clensil), or garlic sprays, caterpillars by Bacillus thuringiensis (Dipel), mites with potassium permanganate (Chondy’s Crystals) or salt solution, slugs and snails with metaldehyde baits (protected from consumption by birds, or other non-target animals) and codling moth by pheromone traps. Neem is starting to take off as an effective non-residual broad spectrum insecticide with pest-repellent and fungicidal properties.
The traditional organic broad spectrum insecticide, pyrethrum can be used against a wide variety of insect pests, including pear and cherry slug. Commercially, pyrethrum is almost always mixed with the synergist piperonyl butoxide. The organic standards demand that pyrethrum be used without this additive as it is a suspected carcinogen. Its inclusion appears to be to give faster knockdown of the pest, rather than increasing its kill rate. Other traditional broad spectrum natural materials include derris, rotenone and ryania.
One pest control method of note that is remarkably effective is making a spray from the target pest and spraying the crop. Caterpillars, slugs, or whatever, are finely minced in a food blender, strained and diluted. The application rate per hectare is extremely low (around 1 kg of insects will treat 30 Ha). The theories as to why this works abound, but to the best of my knowledge no work has been conducted to ascertain which is correct. They include spread of disease from the few organisms infected through the whole population, interference with breeding patterns due to spreading the pests’ pheromones onto all the plants in an area and repulsion due to the odour of deceased organisms of the same type.
Before predators brought the slugs under control in my market garden, I used a similar technique. Hand-picked slugs were killed by dehydration in dry sugar and the resultant slimy mess fermented for a few days in a warm place. The resultant even slimier mess was strained, diluted and sprinkled throughout the market garden area (approximately 0.5 ha). The slug population dropped to a tolerable level in a matter of a week or so and returned only briefly three years later. A repeat application has seen no necessity for further control during a period of ten years. The effect also appears to have spread beyond the area treated.
Much work is being conducted on alternative methods of pest control and most is in the field of biological control. Predators and diseases are being bred for many of the more recalcitrant pests. While this is commendable, it is important to realise that they are generally more expensive than chemical controls and often no more effective than providing a biologically diverse environment that produces its own predators and other checks on pest proliferation.
A very new method involves saturating the environment with pheromones, the chemicals that insects use to find each other for the purposes of reproduction. As biotechnology increases its efficiency, we will likely see the day when it is economical to spray a paddock with a pheromone to dramatically reduce the rate at which specific pests can reproduce. A compelling benefit of this approach is that it is highly specific to the target pest.
Animal Nutrition and Health
We are prone to destroy the beast when it aborts, when it gives midgets, or when it contracts a disease common to ourselves. Destroying the evidence is apparently a more common practice than diagnosing it to find the cause of the abnormalities” — William Albrecht
Several years ago, I was visited by a sheep grazier from South Australia who had converted his property to organic in 1963. I asked him what he did about worms in his sheep. “I used lead,” he said. “For the first three, or four years after conversion, I shot any sheep with worms and I slowly bred the susceptibility out of them”.
This does not mean that organically raised sheep never get worms. Parasitic worms in livestock like fungal disease organisms in the soil, are always present. It is only when they get out of hand that they are a problem. It is very likely that a low level of some of them are essential to the livestock’s well-being.26 The causes of worm problems include stress, genetic susceptibility and malnutrition. One of the main problems of our recent worm control strategies has been the covering up of genetic susceptibility. Prior to the widespread adoption of anthelmintics, susceptible beasts were either culled by the grazier, or Nature. In personal comment on this, a member of the Tasmanian Department of Primary Industry told me that parasitic worms were more prevalent in livestock today than they were prior to the introduction of modern anthelmintics. Since there are no new anthelmintics on the horizon and there is widespread resistance to most of those in current use, we have no choice other than to adopt a more organic approach to the problem.
Apart from genetic susceptibility, probably the most prevalent cause of parasitic worm problems is nutritional stress. The pursuit of higher grass yields, regardless of pasture quality, has led to an overall decline in livestock health. This has been masked, not cured, by ever increasing veterinary chemical inputs. I am not arguing here for the elimination of veterinary chemicals, but against farming strategies that necessitate their overuse.
One useful piece of research suggested by Dr Mike Walker would be to question stock agents about the relative health status of a large number of properties. The pastures of those known to produce consistently healthy livestock could then be analysed for their balance of grass species, grazing management and fertility status of the soils.
Many organic farmers go to some lengths to diversify the pasture species grown beyond the usual grasses and clovers. The ubiquitous flatweed plantain, for instance, supplies more protein to stock than clover. When clover is grazed, the nitrogen fixing root nodules detach and decompose in the soil. The released bacterial protein is then consumed by the plantain before it is in turn consumed by the livestock. New Zealand agronomists have developed strains superior to the wild types.
Other useful species that generally need to be sown include chicories, yarrow and sheep’s burnet. Grass, clover and herb mixtures (herbal ley) are readily available from seed merchants in Europe and North America, but sadly not here as yet.
We have already referred to the necessity of balancing the ratios of the major cations, calcium, magnesium, potassium, and sodium in the soil. Not only does this result in better crop health, but also better animal health. Where the soil is unbalanced, the stock’s nutritional requirements can be balanced by the judicious use of mineral licks, or drenches. Pate Coleby, a Gippsland farmer has pursued this route with some interesting results. When her mineral drenches were compared to veterinary chemicals by the Victorian Department of Agriculture, the results were remarkably similar. One suspects that the minerals were considerably less expensive than the veterinary chemicals.
Many organic farmers the author has spoken to emphasise the importance of avoiding stress to livestock as a prime means of avoiding health problems. For instance, Alfred Haupt, a Bio Dynamic sheep grazier and cropper in New South Wales, talks about the different smell of sheep that are frightened. This smell, he says, is attractive to flies. By minimising loud noises (such as those generated by motorbikes and noisy dogs) he reduces fly strike problems. Those few that are struck are treated with a mixture of pyrethrum and garlic. The pyrethrum kills the maggots and the garlic heals the wound rapidly while at the same time repelling flies that may strike the wound again.
Bert Farquhar, a Tasmanian grazier, planted out walnut trees on his properties Wyambi and Rushy Lagoon. He says that the flies are repelled by the smell of walnut trees. Bert also emphasised the necessity for reducing stress in livestock, not just for health reasons, but but for the all important economic ones. His yards are all set up to allow the stock to be mustered facing into the wind. He says that when the wind comes from behind, it lifts their coats and they become fractious and more difficult to handle.
When lice are a problem, they are readily treated by dusting with diatomaceous earth. This material is the remnants of the skeletons of microscopic organisms, called diatoms. The sharp edges of the particles are a potent and effective insecticide as they damage the breathing tubes of the target organism. On this account, DE is probably not so good for the lungs of beast or farmer. Where lice are persistent, the nutritional status of the stock is probably inadequate. When worms become a problem, a mixture of garlic pulp and cider vinegar (50:50) is an effective vermifuge. We acquired our sheep from a farmer converting to Bio Dynamic. She had phoned me for an organically acceptable alternative to the usual worm drenches. Her lambs had to be agisted during a drought and they became infested with worms. As well as suggesting the garlic/cider vinegar drench, I also offered to buy some of the lambs. She and her veterinary husband delivered the lambs about a fortnight later, and I asked the husband for his opinion regarding the effectiveness of the drench. His comment was that he had never seen such a dramatic overnight change in his life.
Another enthusiastic organic convert, Claude Conlan, told me he had to wait several months following learning about garlic/cider vinegar, before he had the opportunity to try some on his cattle. Not only was he pleased with the result of the drench, he said that when he mustered the stock for a follow-up drench three weeks later, the stock were unusually tractable. When mustering following a conventional drench in the past, the stock had always been quite irascible, he said.
Tasmanian dairy farmer, Ray Mason, applies dilute seawater as a spray to his pastures. In addition, he provides dilute seawater as well as fresh water for his stock to drink. He believes that this is largely responsible for the superb health of his cattle. One unusual side effect of the seawater spray was its remarkable effect on the blackberry rust. On Ray’s side of the blackberry hedgerows, the leaves were unaffected, but on his neighbour’s side, the brambles looked as though they had been sprayed off.
Human Nutrition and Health
There has been a lot of rubbish written and fad-foods consumed in the name of proper human nutrition over the years. We have already referred to Albrecht’s discovery of the apparently better health of humans consuming food growing on the same land that supports the healthiest livestock. That is, the major nutrients calcium, magnesium, potassium and sodium need to be in correct proportion.
Eve Balfour in her book, Soil and Health, drew similar conclusions. She further concluded that the best human health was exhibited by populations eating whole food regardless of whether it was a vegetarian, meat, or fish based diet. Much of modern nutritional problems stem from diets that are unbalanced and consist of excessive amounts of fat and processed food. For instance, the human organism absorbs cadmium more readily when zinc is in short supply. Zinc accumulates in the bran of the wheat berry, cadmium in the starchy gymnosperm. The production of white flour entails the removal of the bran carrying the zinc, leaving the gymnosperm carrying the cadmium. In other words, consuming white flour is likely to increase your cadmium absorption when compared to consuming wholemeal flour.
A persistent claim of one sector of the green movement is that modern synthetic pesticides in the diet are a major cause of human cancer. There is precious little scientific evidence for this. On the other hand, there is scientific evidence in favour of other causes; in particular, stress. The persistent and possibly erroneous claim that pesticide residues in our food are exposing us to an unacceptably high risk of cancer itself must cause stress. Since we know that stress increases the risk of cancer, perhaps those making the claim are themselves inadvertently increasing the risk of cancer.
We are not trying to imply that growing systems have no effect on human nutrition and health, we are just trying to put it in perspective as part of a larger picture. Given the conclusions drawn concerning livestock nutrition in the previous chapter, it seems likely that the method of growing our food does have an influence on its nutritional qualities and hence its effect on human health. However, this must be balanced against the fact that these effects are probably masked by overall bad food consumption habits and arguably poor medical practises.
One interesting trend over recent decades is that sperm counts of Western males has declined considerably. The average American male is apparently functionally sterile. This does not mean that they are incapable of impregnation, but that many more attempts are now required for success. Thirty men attending the AGM of the Danish National Board of Organic Farmers were asked to donate sperm for comparison by the Danish State Hospital. They all had diets that included at least 50% organically grown produce. Their sperm counts averaged 104million per millilitre compared to the accepted average of 50-55 million. While the sample is too small to be definitive, it has led to a proposed three year clinical trial.
Conversion to Organic Farming
Pasture is very easy to convert to organic production methods. Quite small amounts of pelletised poultry manure, or liquid fish have proved capable of stimulating the soil biology in a matter of weeks. We have seen the root depth increase from around 50 mm to 300 mm after twelve months. This allows the grass roots to reach nutrients they would otherwise be unable to obtain and pulling of the grass in winter is eliminated. The consequent increase in humus level from around 1.5-2.5% to 4-5% increases water holding capacity from 12-38 mm to 100-150 mm. This increase naturally improves grass production and extends the growing season in dry weather. It is important too, to realise that when humus levels are below 2.5%, the cationic nutrients, calcium, magnesium, potassium and trace elements, leach. When the humus level is a more acceptable 4-5%, leaching ceases to be an issue.
The first indicator that the biological activity is on the upswing is the presence, in appropriate soil conditions of earthworms. There are instances of pasture without earthworms and they benefit enormously from their introduction. Tasmanian farmer, Bert Farquhar, doubled his stock carrying capacity when he introduced European earthworms to his properties Rushy Lagoon and Wyambi. It is pointless to look for earthworms when the soil is too hot, or too dry. Generally, their activity is at a peak in mid spring, when soil temperatures are between 10 and 20°C.
Beware of people selling earthworms. There are two main sorts, pasture worms and manure worms. The worms propagated by worm farmers are nearly always manure worms. They are adapted to very high organic matter levels and do not consume soil. Pasture worms in the typical worm-farm situation die out after a time. Nearly always, earthworm absence is a symptom of inhospitable soil conditions. They require the pH to be between 5 and 8 and for there to be adequate organic matter and moisture. Where they must be introduced, it is best to cut turf from pasture with earthworms and place pieces, grass side down, at 10 metre intervals to seed the pasture needing them. The pieces are generally about 100 mm by 150 mm. There are manufacturers of specialised turf cutting machinery in New Zealand.
A similar response to organic fertilisers has been noted in pome fruit orchards. Soil that showed no sign of earthworm activity for decades became liberally covered with worm casts in the spring following winter application of pelletised poultry manure. Kiwi fruit orchards in New Zealand responded similarly to a soil drench of liquid fish.
Many field crops have also responded well, but the heavy feeding, long season crop, potatoes has been disappointing. Sap analysis showed that pelletised poultry manure was supplying adequate levels of nitrogen and potassium, elevated levels of calcium and trace elements, but very poor mobilisation of phosphorus. This would seem to indicate that a mixture of pelletised poultry manure and superphosphate (or rock phosphate) would give better results. A crop receiving a mixture of 1 tonne per hectare of poultry manure pellets and 300 kg per hectare 11:12:19 outyielded one receiving 1200 kg per hectare 11:12:19. The potatoes that received poultry manure pellets were hardly affected by either blackleg and blight. The potatoes grown on 11:12:19 alone were badly affected.
Inspection of the soil these various potato crops were growing in showed little sign of earthworm activity when compared to pasture, pome fruit orchards and a hop field trial. While potato farmers acknowledge that the best crops are grown coming out of pasture, very few growers now include a pasture phase in their crop rotation. It is highly likely that the reduction in earthworms in cropland is due not only to continual cropping and subsequent excessive tillage, but also the soil compaction created during winter potato harvest. One simple solution to the latter problem would be to harvest the potatoes in autumn, when the soil is still dry and store them in sheds until needed. This would also allow the sowing of a green manure crop to reduce winter soil erosion which is quite dramatic when viewed from the air over the sea near river estuaries.
The increase in calcium uptake as a result of the addition of organic manure to potato crops is an indication that the potatoes will store better. One of the most frustrating problems in recent years has been the poor quality of potatoes grown under a conventional regime.
The summer of 1992/3 was particularly wet in northern Tasmania and the tops of most potato crops died off very early from the fungal disease, target spot. Two crops, both grown on conventional fertiliser, were treated with foliar sprays of liquid fish in one instance and dilute pig slurry in the other. Both crops lived a good six weeks longer than the untreated crops and outyielded them by a good margin. Both the treated and untreated crops received the usual fungicide program.
We believe that there is a potential to increase potato yields and quality by a judicious mixture of organic and artificial fertilisers. This would allow some land to be returned to pasture, which in turn would enable the humus level and consequently the fertility of the soil to be built up. The pasture phase would not necessarily require stocking with animals. A cow grass, or lucerne pasture could be mowed and the dried, shredded material used as a substitute protein source in place of pelletised poultry manure.
It used to be that permanent pasture lasted for centuries. These days, many farmers consider themselves lucky if “permanent” pasture lasts for a decade. What has gone wrong? First, the pasture is regularly fed with superphosphate, keeping the bulk of feeder roots close to the soil surface. This leads to very shallow roots on the pasture grasses. Since the roots can only exploit what they can reach, they must subsequently be continuously fed to maintain production. The shallow roots also lead to a drought-prone condition and the grazing animals readily pull the grass, roots and all, from the ground. This leads to gaps in the sward that are repopulated by weeds, such as thistles.
A further problem arises if urea is used to boost production. Any nitrogen in excess of the crop’s needs is utilised by the soil micro-organisms. In order to balance their diet, they consume the organic matter in the soil. This in turn leads to reduced humus levels and fertility, necessitating increasing amounts of urea to maintain the same grass yield.
Organically managed pasture in good heart has deep roots and high organic matter levels. Production is maintained longer in dry conditions and it resists invasion by undesirable weeds. Water falling on it is more quickly absorbed and more is retained. Fertiliser amendments, including lime, are needed only infrequently.
Converting existing pasture to a more organic system is relatively easy. First, you need a soil test (or tests) to establish the balance of calcium, magnesium, potassium and sodium. Nearly always, the required balance can be achieved with dolomite, or ordinary limestone. If potassium is deficient, amendment should wait the outcome of a year, or two of conversion, as potassium levels can rise dramatically in response to organic fertilisers. Probably the cheapest and simplest amendment to use at this stage is fish emulsion. Very little (10-20 l/ha) is required as you are feeding the soil microorganisms, not the grass. It is applied with a boom spray, or better a field jet. On Flinders Island, the graziers call this a rooster tail because of the shape of the spray. The field jet allows a coarser spray, less prone to wind effects and doesn’t have the fine filters of a boom spray. If you do use a boom spray, removing the filters will allow a faster application rate.
An alternative to fish emulsion is pelletised poultry manure. Only 3-400 kg/ha is required.
The first effects of organic manuring observed by most farmers are preferential grazing of the treated areas and an improvement in stock health. Digging a spit of soil in treated and untreated areas several weeks after treatment shows improved root depth, increased clover nodulation and better moisture retention. After several years of such a regime, you will find it no longer necessary to apply the fish emulsion, or poultry manure annually. You will have a self-stoking cycle going.
The period between amendments will vary considerably, depending on soil-type, pasture species mix and what is being exported from the farm. Clover acidifies the soil and promotes leaching of calcium and magnesium. The rate at which this occurs is a function of the rainfall and proportion of clover in the pasture. If milk is being exported, this will add to the calcium drain. Wool, on the other hand, will reduce sulphur quicker. Much animal protein consists largely of carbon, hydrogen, oxygen and nitrogen, all of which can be supplied from the atmosphere.
Maintaining pasture also requires management other than fertiliser inputs. Pasture production and health are optimised when grass length is maintained between 25 and 150 mm. If this cannot be achieved with stock and fodder conservation, then mowing paddocks that are long is required. Regular harrowing will also assist aeration of the top few centimetres of soil and increase the rate of breakdown of animal manure.
They are a savage, wicked brood… all experienced husbandmen… would unanimously agree to extirpate their whole race as entirely in England they have done the wolves, though much more innocent and less rapacious than weeds. — Jethro Tull
Most farmers have come to rely very heavily on herbicides for weed control. While on the surface, chemical weed killers appear to provide many benefits, they are also a two-edged sword. Some farmers have discovered that when soil humus levels fall to a very low figure, herbicide residues in the soil are reactivated to the detriment of the crops. Some herbicides are ineffective in soils with too high organic matter levels. Given the manifold benefits of high organic matter levels in the soil, it would appear to be a poor farming strategy to limit them to maintain the effectiveness of herbicide.
In the winter of 1994, Monsanto wrote to many farmers (including the writer) offering a “free” cricket hat in return for buying their product and advising farmers to use a mixture of Ramrod Flowable® and Stomp® on their onion crops. A few weeks later, a letter arrived apologising for any inconvenience this advice had caused; it was incorrect. The effect of this mixture was not stated, but one imagines it was deleterious. Given the volume of sales literature that crosses my own desk, it is not too hard to imagine some farmers missing the second message, particularly since the letter was headed “Roundup® and Your Free Cricket Hat”, hardly designed to arouse the farmers’ attention to problems caused by Monsanto’s bad advice.
Invariably, some plants are resistant, or immune, to any particular herbicide. This has given some weeds that were previously innocuous a competitive edge, necessitating the use of yet another herbicide. As well, some herbicides, notably glyphosate, appear to inhibit uptake of trace elements by crops. Above all, the observation I have made on many farm walks is that organic farmers appear to have less weed problems than their conventional counterparts.
There are several strategies adopted by organic farmers to control weeds. Probably at the forefront, is the maintenance of a fertile soil. Many weeds are a response to less than ideal soil conditions for crops. Dock and wire-weed, for instance, are a response to compacted soil. Thistles are a response to under, or overgrazing and to a lesser extent, excess nitrate levels in the soil. Cape weed is a response to low soil fertility. On my own farm, we had a one acre paddock of vegetables for a couple of seasons, before returning the paddock to pasture. For the ensuing four years, you could clearly see where the footpaths between the raised beds had been by the number of docks in the paths. Gradually, the docks broke the hard pan and in so doing, reduced their competitive edge and the grass sward is now nearly uniform.
Victorian farmer, Frank Chenowyth, farmed conventionally from 1954 to 1984. He was facing mounting stock health problems and decided to devote the money he normally spent on super to trace elements. Apart from a dramatic improvement in stock health, he also noted the proliferation of desirable pasture species at the expense of weeds without the necessity for resowing.
Tasmanian dairy farmer, Joe Gretchman, takes a different tack. While most farmers have a profound hatred for the toxic weed ragwort, Joe is “letting Nature take its course” despite purchasing “the ragwort capital of northern Tasmania”. He estimates that slightly less than 5% of the pasture is occupied by ragwort plants, so the decreased yield caused by their occupying soil that would otherwise be growing grass is negligible. Joe also pointed out that the roots of the ragwort go down between one and two metres. They absorb nutrients that the shallower pasture grasses cannot access and deposit them at the soil surface when they drop their leaves. Of course it is essential that ragwort that might end up in hay be removed.
When Tim Marshall visited Queensland Bio Dynamic grazier and cropper, Alfred Haupt, he remarked that the thistles looked as if they had been recently sprayed with herbicide. Alfred explained that he flooded the paddock and left the water until the clover was almost drowned. The thistles were less resistant to waterlogging than the clover and expired.
These examples were given to illustrate the wide variety of attitudes and strategies adopted by different farmers. In organic farming, weed control is rarely oriented toward the rather unrealistic goal of total elimination. Many weeds can be kept to tolerable levels without resort to poisoning, or excessive cultivation.
Cultivation remains the primary method of weed control in cropping. It has been pointed out that cultivation is responsible for much damage to soil structure and contributes to soil erosion. However, organic farmers defend their preference for cultivation to herbicides. They point out that organically managed soils are more tolerant of cultivation since their structure is better than soil under a conventional regime. As well, their crop rotations are generally more diverse and almost invariably include a pasture phase which all contribute to lower weed infestation rates.
Many organic farmers use alley cropping to minimise soil compaction and increase yields. This entails the creation of permanent raised beds with the tractor tyres always in pathways between. The structure of the soil in these raised beds is never compacted, reducing the need for excess tillage. Weed control implements are chosen for their ability to minimise soil inversion. There can be more than two billion weed seeds per hectare in the soil, some 15% of which are capable of germination. Shallow, non-inverting tillage reduces the number that germinate. Deep tillage to reduce hard pan is virtually a once off operation immediately prior to the formation of the permanent raised beds.
Choice of crop variety can play a role in weed control. Many organic wheat farmers grow older, long-straw varieties in preference to the more recent short-strawed varieties. These provide more shading at the soil level and this reduces the ability of weeds to compete. While the conventional farmer perceives little virtue in growing straw at the expense of grain, to the organic producer, straw is a valuable resource as it is a source of organic matter to improve soil structure. Since many organic wheat farmers also undersow the crop with clover, this also reduces weed competition as well as providing nitrogen.
Conventional wheat farmers are no doubt raising their eyebrows at these strategies, since they also reduce crop yields. It is important to emphasise that the farmer’s goal should not be yield at the expense of everything else. A grower losing 5 kg of topsoil for each kilo of wheat grown is living off his, or her capital. No business can expect to survive in this circumstance. It was enlightening to follow a dialogue between organic and conventional wheat growers at the 1990 organic agriculture conference at Adelaide University. The organic growers reported little or no problems with fungal diseases, such as take-all and rust. This was received with some scepticism by the conventional growers. The most important point here is that organic wheat growers make incomes that are almost identical to their conventional counterparts.
While at the 1990 organic agriculture conference in Adelaide, participants went on several farm walks. One of the most interesting to me was a Bio Dynamic market garden, where for the first time I saw a flame weeder. This device has an LPG gas burner underneath a shroud that reflects the heat onto the soil and emerging weeds. The weed seedlings are raised to a temperature of around 60°C and this coagulates the protein in the sap, effectively killing them. The grower said it cost $40/ha to flame weed compared to $70/ha for herbicide. German farming implement designer, Bernward Geier, pointed out several aspects of the machine the farmer was using that could be modified to improve its efficiency.
New Zealand vegetable producer, Marinus La Rooj also uses a flame weeder for pre-emergence weed control. He places a small sheet of glass on the seed bed immediately after sowing a crop. This accelerates germination under the glass, so when the crop seeds emerge there he knows it is time to flame weed. On Marinus’ farm, post emergence weed control is with a tickle-weeder. This implement consists of many flexible stainless-steel tines that vibrate as they are dragged across the soil. Well-established crops, such as carrots, pumpkins, lettuce and brassicas push the tines to one side and receive remarkably little damage. Weed seedlings at the white-wire stage are dragged from the soil to die.
Another weeding implement favoured by organic vegetable producers is the brush-hoe. This resembles a miniature street sweeper, the slowly rotating bristles penetrating the soil to a depth of about 25 mm. This works on more established weeds than the tickle, or flame weeders. The leaves are pulverised and left on the soil surface to act as a mulch, reducing further weed seed germination and reducing moisture loss.
A friend establishing a vineyard trialed three approaches to weed control; weed mat, hay over newspaper and herbicide. The hay and newspaper mulch was by far the most effective, though also the most labour intensive. The weed mat was much quicker to apply, but appeared to reduce the water-infiltration rate from the drippers. Also, many weeds had their roots under the mat and grew outward under the edges. The herbicide-treated rootlings were the least vigorous.
Mulching perennial crops by hand is torturous and back-breaking and that is not a recipe to delight the average farmer. However, there have been a number of implements developed to shred mulch materials and deposit them alongside the crop. Typical mulch materials are newspapers, straw and hay bales. Queensland cane growers have remarked the results obtained by depositing crop trash in situ versus burning. It has reduced nitrogen leaching, improved weed control, improved water infiltration rates and moisture retention.
A novel approach to mulching was taken by the Tasmanian Department of Primary Industry. They developed a system whereby oats were sown into an onion crop. The root system of the oats reduced the problem of soil washing in the winter rain. Often, erosion in heavy rain is sufficient to remove immature onion plants. In the late winter, or early spring, the crop was sprayed with a selective herbicide to kill the oats. The dead oats acted as a mulch for the onion crop, obviating the necessity for continual herbicide sprays that are usually necessary.
A more organic approach was that taken by the CSIRO and its use of sub-clover. Under typical Australian climatic conditions, sub-clover is summer-dormant, so summer maturing crops planted into a sward do not suffer from competition with the clover. The clover takes off in the winter months to fix atmospheric nitrogen and its residue acts as a moisture-conserving and weed-suppressing mulch in the summer months.
Grazing to control weeds in perennial crops is an effective way of achieving multiple land-use. Australian Hop Marketers at Gunns Plains in Tasmania’s north west use sheep to control weeds for much of the year. The hop vines are only grazed by sheep when they shoot their young foliage in the spring. This period is only a few weeks. For most of the year, the hops are either dormant, or too mature to interest the sheep.
Like their conventional counterparts, most organic farmers use traditional cultivation equipment for weed control. Many weed seeds need light in order to germinate and cultivating in the dark can reduce weed seed germination rates by 98% according to German research. Weeds such as fat hen, cleavers and chickweed were severely checked. Others, such as toadflax and wild chamomile were stopped completely. Conversely, if you want to stimulate weed seed germination to reduce the number of seeds, it is best to cultivate in the middle of a bright sunny day. Unfortunately, weeds that multiply vegetatively, such as couch grass, can increase through night-time cultivation. This research opens many possibilities, such as the development of light-proof covers for harrows that would allow arable work to remain a daylight occupation.
While hand tools are little used these days by conventional farmers, they have a place on many organic farms. This is not because organic farmers are Luddites, but because they are an economical alternative to power tools, large and small. One such is the GR Wheel Hoe manufactured and marketed by Gundaroo Tiller. The oscillating stirrup hoe is very efficient and because of its curved bottom and vertical sides, allows working very close to plants without risk of damage to roots. It is at least as efficient for weed control as a walk-behind rotary hoe, much quieter and doesn’t consume any fuel. Gundaroo Tiller also market Eliot Coleman’s Gung Hoe. Eliot developed this hand-held hoe during his thirty or so years of market gardening. He discovered that using the hoe more like a broom, sweeping the blade through the soil, just under the surface, was much more efficient than the chopping action of conventional hoes. This is because chopping uses wrist muscles. The Gung Hoe approach makes more use of the shoulder muscles, reducing operator fatigue. As well, the Gung Hoe is angled precisely for optimum efficiency. Conventional hoe blades are at a 65° angle, the Gung Hoe 70°. The blade is reduced in width to reduce friction and the shank spot welded to the upper face of the blade for the same reason.
A weed control system in development is the use of myco-herbicides. These are plant pathogens, often fungi, and they are applied with regular spray equipment. Most are highly specific, attacking only particular weeds. It appears likely that combinations of myco-herbicides will be developed to more closely imitate conventional broad-spectrum herbicides. Many living organisms generate natural toxins that could be developed for use as herbicides, just as pyrethrins from Chrysanthemum species have been used to poison insects. Such materials would have an advantage over myco-herbicides in that they are not living organisms and therefore could not proliferate and spread in the environment to attack non-target plants. They would also be less affected by weather conditions that can inhibit the effectiveness living organisms. One that was developed in the United States had its origins in the Tasmanian Bluegum (Eucalyptus globulus) but has yet to reach Australia.
Also in this vein, many plants produce chemicals that inhibit other plants living nearby. They are called allelo chemicals and it is likely that these are responsible for many of what organic gardeners call companion planting effects and scientists call allelopathy. There are two approaches to utilising these substances. While the production of allelochemicals is very common among wild plants, this ability appears to have been unintentionally bred out of almost all our cultivated species. Perhaps there is scope for breeding the ability back in by cross breeding with the wild ancestors of our crop plants. Alternatively, allelochemicals could be used to develop a new class of herbicides. It is interesting to note that allelochemicals have a more potent effect in soils low in humus and bacterial activity. This could explain why weed competition is less of a problem to organic farmers.
A New Zealand company, Waipuna Systems of Aukland, is pioneering the use of steam weeding. Their steam weeder can be used in any weather and is effective almost immediately, the results being directly comparable to glyphosate. The New Zealand Crop and Food Research Centre carried out trials in 1993 that showed all annual and some perennial weeds were completely killed. Dock and dandelion took 40 days to recover.34
Other emerging technologies include electrostatic discharge, laser and microwaves. These are all similar in their effect to flame weeding with its limitations on use in established crops. As well, their effectiveness is dependent on factors such as the duration of exposure; they can be very slow. Perhaps they will become more widespread as they are further developed.
Farming for the Future
Once the soil is exhausted, you’re on an ash heap. You don’t know what’s missing except that nothing grows. The mysteries of creation haven’t all been put under button pushing technology” — William Albrecht
Having discussed some of the many factors affecting farm production systems, it remains to provide some pointers to how to implement them. Many farmers have found the hardest part to using more organic techniques in their farming is the hostility from agricultural extension officers, consultants, fertiliser salesmen, spray salesmen and their farming colleagues. Some farmers prefer to keep their organic practises a secret to avoid this. Equal ranking is often given to maintaining self-confidence. The conversion phase from conventional to fully organic can take several years while the soil biology restabilises. This appears to be more of a problem in annual cropping than with perennial crops.
There are few sources of information, one of the main reasons for writing this book. There is considerable literature of overseas origin, but this was written for quite different agricultural conditions than those experienced in Australia. There is often an assumption that organic farming, because it originated overseas, is not practised so well here. This is untrue and there are many fine examples of organic farms unequalled in Europe, or North America. Unfortunately, the numbers are smaller than overseas and this is probably why there are less books written here. As well, little of the literature takes the middle ground as we have attempted to do in this volume. Most writers are ideologically committed to an all or nothing approach. This can also be a problem when approaching organic farmers and farm advisers. When my friend Wesley Hazell started a 20 acre Bio Dynamic pasture trial, a BD farmer objected “because he doesn’t have the right consciousness”. Wesley’s family owns several properties, each farm having its own manager, and it was this, the fact that Wesley doesn’t personally operate the farm in question, that the Bio Dynamic farmer was referring to. As well, the workers on the farm where the trial is taking place objected, “because you can’t grow grass without super”.
Wesley could not be said to be a typical farmer; his family owns several farms and a major earthmoving business. But he is typical of the new generation of forward thinking farmers. About a decade ago, the Tasmanian Rural Youth organisation invited a speaker to one of their meetings to talk about organics. The speaker was a backyard organic gardener, who obviously knew little about farming. When some of the audience jeered the poor chap, Wesley stood up and chastised them, saying “in ten years time we’ll all want to know about organic farming. This guy’s talking about what our customers will all be wanting”.
I have heard many variations on this theme from farmers all around Australia. They are aware that their income is dependent on customers buying their produce. To remain viable, farmers must provide what the customer demands. While it will be pointed out that farmers have been doing this, what the customers want is continually moving target. One example of this is the dramatic reduction in demand for potatoes. Much of this is due to changed food habits, such as the increased consumption of rice, but some of the blame must lie with the appalling quality of potatoes proffered for sale. A typical bag of potatoes from the local supermarket recently revealed all of the potatoes had bruises, several were green and several infested with potato grub. Peeling wastage was around 20%.
Another example came from some Tasmanian Department of Primary Industry research into consumer preferences for apricots. They were presented for tasting as under-ripe, ripe and over-ripe. The customers overwhelmingly preferred the ripe fruit. The stores only stock under-ripe, because it lasts longer. It lasts longer because the customers don’t want to buy it! They buy other fruit instead. This situation is likely to persist while farmers continue to accept what happens to their fruit after it leaves the farm gate. One perennial problem in this regard is farmers who pick early fruit while it is unripe in order to obtain the premium prices offered for being first in the market. This has the effect of lowering demand for a considerable period until the customers forget their disgust at the lack of flavour in their purchases. One group of plum growers who were persuaded by a colleague to hold off until their fruit was truly ripe, found shoppers reluctant to buy their fruit. They had been put off by the under-ripe early fruit in the previous fortnight. These farmers overcame the problem by going into the supermarkets and fruit dealers to give away samples of their fruit as a promotion. Within a week, they were selling all of their fruit for top prices.
It should be clear that customers have a number of criteria that they apply when parting with their money to buy produce. The more of these criteria that are met, the higher the price they are willing to pay. The quality issues are flavour, appearance and residue status. While until recently, appearance was the only criterion, all are now important. One exporter received a severe shock when a consignment of shallots was rejected for import into the United States. The reason was an unacceptable level of fungicide residue. Not only was that sale lost, but other orders were cancelled as a result of the incident. The fungicide in question was only used pre-plant under special permit, as it was not a registered material. This left the exporter with the problem of finding an alternative strategy for white root rot control and new markets in the meantime.
Credentials and Credibility
This is the era of specialisation. From one point of view, this has resulted in enormous progress. We can now place fresh raspberries on markets thousands of miles away, plough a thousand times as many acres in a day as we could fifty years ago, accurately forecast crop yield halfway through the growing season, make telephone calls from the tractor, measure the exact amount of irrigation to apply and when, determine the harvest date for obtaining optimum quality of produce when it reaches the market and many other wonderful things. Without specialists, these things could not be.
There is, however, a downside to specialisation. In order to become an effective specialist, a person learns from a teacher experienced in a particular discipline. This entails ignoring almost everything else that could reduce the time needed to take on board all the information accumulated by the profession. Each profession has developed its own language to communicate its ideas quickly and efficiently. Unfortunately, it also means that the ideas of one discipline cannot be effectively communicated to a person specialising in another. The languages are different.
This would not be such a great problem except that an unimportant discovery in one area of research can be of world shattering importance in another. Since there is no communication between the disciplines, it is a long time before some heretic makes the connection.
Tolstoy wrote, “I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives”. James Gleik puts it only a little less elegantly. “Shallow ideas can be assimilated; ideas that require people to reorganise their picture of the world provoke hostility”.
Bringing this back to farming, we have agricultural scientists split into numerous disciplines. A soil scientist might develop a fertiliser program that increases grass production. The stock grazing the grass become prone to disease. The soil scientist, if he becomes aware of the problem that has arisen, would say “that’s not my problem. That’s an animal physiology problem”. Apprising an animal physiologist of the effects of the fertiliser program on animal health elicits the response, “That’s not an animal physiology problem; it’s a soil science problem”.
The person most likely to have made the connection between the fertiliser program and animal health problem would be the farmer. If he tells the soil scientist, the soil scientist will likely tell him he doesn’t understand soil science. The response from the animal physiologist will in all probability be similar.
The manufacturer of Vitec fertilisers, Ted Sloan, has degrees in Agricultural Science and Agricultural Engineering and spent several years as an agricultural extension officer in New Zealand. He says that it is his “lasting shame” that he ignored the observations that his farmer clientele communicated to him. “The observations I was trained to ignore have turned out to be of immense and lasting value”. Ted also had the ignominy of becoming a farmer and attempting to put into practice the ideas he had been taught. They did not work. What did work was applying ideas that farmers had observed worked best.
There is no doubt that our agricultural scientists have done an excellent job within the confines of their respective fields. What we need is for that work to be integrated by imaginative non-specialists in order to create a new agriculture. One that satisfies the needs of farmers and the wider community.
Miguel Altieri illustrated this with a diagram of three overlapping circles. The diagram illustrates the three main facets of society: economic, social and environmental. Only pursuits that take account of all three are truly sustainable. For instance, our food production system might produce economic profit, but if it damages the health of farm workers (a social issue) or destroys the riverine system (an environmental issue) it will fail.
So how do we better integrate the results of the many specialised disciplines, farmer observations and the needs of the wider public in order to create a new agriculture? There is no simple answer to this question, the most important raised in this book. However, the author was involved in a discussion forum held to allow the greenies, forestry workers and general public to discuss their concerns. The finale to this forum, held over several weekends, was a forest walk to look at the source of the debate. During the barbecue lunch that followed the walk, the most typical comment heard was “I never really understood their point of view before”. From a hostile beginning, the outcome was, as hoped, one of healthy debate where fresh information from outside the confines of the interest group led to deeper understanding.
We all to some degree or other work and live within the confines of our interests, unaware of the wider ramifications of what we are doing. It is only when we can take a step back away from this limited arena that we can gain the wider perspective needed to perceive that what we do affects us all. How many critics of farming have walked a farm and discussed the farmer’s problems with the farmer? How many farmers who criticise the poor outcome of applying an agricultural scientist’s advice have bothered to query the researcher to discover exactly what went wrong?