Whither Farming: Biodynamic, Organic or Science?
Organic and biodynamic farming are currently on the rise across Europe. The underlying concepts, however, are hardly based on scientific data but rather on ideological belief, as Scottish plant biologist Anthony Trewavas comments on our previous editorial "Occultists conquer Kassel University".
(Apr 24th 2007) In 1926 Rudolph Steiner gave a series of anthroposophical lectures, which form the basis of biodynamic agriculture. Steiner believed that cow manure contained vitalistic energy generated by cosmic forces; these were focussed via a cow's horns onto its intestine and impregnated soil with fertility. Consequently cow's horns containing manure or silica are buried in biodynamic fields for at least six months. (Analyses at Rothamsted showed that indeed after six months these horns contained......rotted manure and unchanged silica). Other biodynamic features include composting certain herbs in cows' intestines or stags' bladders, which are then used to energise compost heaps, sowing crops by moonlight, etc.
Steiner's magical approaches, based it is thought on German peasant recipes, were formulated in the belief that man-made chemicals of all kinds including soluble minerals damaged and polluted the soil. Although organic agriculture developed later and discarded (rightly) Steiner's occult forces, certain features are found in common between the two. These include (1) Prohibition of all man-made chemicals including soluble minerals, herbicides and synthetic pesticides, (2) A belief that healthy soil is essential to produce healthy crops (and thus healthy food), (3) That farms should be responsibly self-sufficient because basic agricultural resources are running out. Thus crop nutrients were to be provided only by animal manure made on the farm or green manure made by ploughing in nitrogen-fixing legumes, (4) Animal disease to be treated by natural (often homeopathic) means. The farm was to be viewed holistically although this term is often used as a mantra rather than reflecting understanding.
The early founders of organic agriculture in the UK were flexible, incorporating scientific knowledge as it developed. But later more ideologically rigid supporters elevated the above assertions to an almost religious status. The true UK heirs to common-sense, responsible farming are now to be found in the LEAF farming organisation and their web site (
www.leafuk.org) outlines their farming methods.
Better soils?
Lawes and Gilbert established the Broadbalk experiment in 1845. Winter wheat has been grown continuously in two fields; one field has received only soluble minerals, the other only animal manure. Throughout the 161 years, yields have remained identical between the two fields and are similar to the UK average. However, the amount of manure required to achieve yield parity is much higher than farmers would normally use and consequently nitrate pollution, as the run-off is much higher than the minerals-only field. The soil organic content of the manure-only field has doubled and even that of the mineral-only field has increased by 20% in 161 years. Although crop rotation is absent, the biodynamic and organic contentions that minerals damage the soil and that yields are related to soil organic content is clearly contradicted. A period of 161 years is sufficient to establish that conventional farming is sustainable.
Many measurements indicate that, at least in commercial practice, organic yields are substantially lower than an equivalent conventional farm. Recent UK estimates indicate that average organic wheat yield is 4tons/ha; conventional 8tons/ha. The Haughley experiment organised by the Soil Association (the primary organic association) in the UK ceased in 1965 (after 35 years) because yields of wheat, barley, beans and eggs were substantially lower than local conventional averages. Organic methods rely on mineralisation of manures. But mineralisation is slow, continues throughout the season and does not synchronise with the mineral requirements of rapid canopy development in springtime. Careful application of soluble minerals can match crop growth requirements more exactly and engender more reliable yields, crucial for farmers' incomes. Green manure depends on N fixation in legumes but the apparent yearly variation can be 3 fold because of temperature, soil and rainfall unpredictability.
All agricultural produce sold off-farm contains minerals (N, P, Mg, Ca); unless these are replaced from sources
outside the farm the soil is mined and becomes deficient. Analyses at Rothamsted Experimental Station (Hertford, UK) indicated the majority of organic soils examined were phosphate deficient. Although organic regulations permit the addition of a number of crudely-mined minerals such as phosphate rock or sylvinite (i.e. potassium chloride), a number of these are known to contain cadmium as contaminants. Manure and straw can be purchased from conventional farms. But both these are produced by conventional farms using mineral application, a form of farming that organic associations and institutes attack as not being sustainable and conflicting with the ideological requirement that organic farms must be self-sufficient! Further complications result from the fact that animal manures can vary enormously in their potential mineral content but represent the primary source of P on any organic farm.
Although it has been claimed that organic soils are more fertile, these are based solely on measurements of microorganism numbers. But a group of UK organic and conventional researchers concluded rightly that, "soil fertility is defined as an ability of a soil to provide the conditions required for plant growth. Although nutrient management in organically managed soils is fundamentally different to those managed conventionally, the underlying processes supporting soil fertility are not". (Quotes in Trewavas, 2004). UK investigations reported highest bacterial numbers on fields using Integrated Farm Management (IFM; see
www.leafuk.org for IFM regulations); only in fungal numbers were organic soils higher. Organic contents of most conventional and organic soils are little different because manure on any mixed farm is usually spread to save the farmer money on fertiliser.
A mosaic of habitats is best for biodiversity on any farm. Weeds are certainly higher in organic fields and these again reduce crop yield but other elements of biodiversity are far less certain. When comparisons have been made between well-managed IFM farms with a mosaic of habitats (such as LEAF), differences are no longer perceptible and this applies equally to animal care regulations. Not to treat diseased animals properly because of ideological considerations can be regarded as cruel.
Healthy soils, healthy food?
The UK Food Standards Agency (with other agencies across Europe) has concluded that no health benefits are gained from organic food. Occasional claims are made that organic produce has trivially higher amounts of some vitamins and minerals but exacting measurements have usually found no difference. Different cultivars of any fruit or vegetable species can vary at least 10 fold in vitamin content, carotene (vitamin A precursor) in carrots, for example, can vary 50 fold. But who buys produce on this basis? Mineral content is equally variable. The public can distinguish the taste of fresh from stale produce but not organic from conventional when presented in the same way.
The public have been exposed to an unremitting propaganda about synthetic pesticides from various scientifically unqualified campaigning groups. But the major chemical exposure of any human is to the estimated 100,000 natural pesticides produced by all plants that efficiently kill insect herbivores. When tested toxicologically, the majority of natural pesticides consumed daily are carcinogenic, others are oestrogen mimics or inflict testicular damage, nerve toxins, teratogens, chromosome breakers, or damage the blood, skin or thyroid. Several thousand natural pesticides are consumed daily but despite outweighing synthetic pesticide traces by more than 20,000 fold, known effects of natural pesticides on human health are not common. Nerve toxins in potato and cucurbits have killed at least 30 people or induced unpleasant vomiting attacks for thousands. But the inadvertent elevation responsible was only 5-10 fold. Psoralens in figs, celery and parsnips are known to commonly cause skin blistering. During domestication the search for higher yield reduced natural pesticide contents in most crops making them safer for human consumption but more vulnerable to insect damage and necessitating adjuncts of synthetic pesticides. Limited evidence suggests that organic methods elevate natural pesticide contents.
Some 200 cohort investigations have established that a diet high in fruit and vegetables cuts cancer risks about in half. All these investigations used conventional fruit and vegetables containing synthetic pesticide traces. Since price is a strong determinant of consumption, purchase of higher-priced organic produce will reduce overall consumption and thus increase cancer risks for those who buy organic in the belief that it is healthier. No one food contains all the necessary constituents for good health, consequently only diets can be healthy and a conventional diet balanced between cereals, meat or fish and fruit and vegetables contains everything necessary. Unfortunately only 20% of the population eat sufficient fruit and vegetables for protection.
Western cancer rates have been in overall decline for at least 50 years and life expectancy continues to increase linearly as it has from 1840 onwards. Farmers who receive the highest exposure to synthetic pesticides have overall cancer rates about half that of equivalent population. World food prices have dropped by half in the last 50 years as the result of efficient conventional agriculture. Going organic worldwide with its lower yield would necessitate ploughing up the remaining tropical forest with severe consequences for global warming!
The scientific references that establish the above can be found in:
- Trewavas, A.J. Crop Protection 23 (2004) 737-781.
- Trewavas, A.J. (2005) Annals Applied Biology Letters number 56.
