David Green discusses the reasons behind why farmers are keen to adopt biotech soybean crops.
The global uptake of agricultural biotechnology has been impressive. In 2002, the worldwide area of biotech crops was 12 per cent higher than in 2001 at 58.7 million hectares grown by nearly six million farmers in 16 countries. Apart from the USA, Argentina and China, other countries growing biotech crops during 2002 include South Africa, Australia, Mexico, Bulgaria, Uruguay, Romania, Spain, Indonesia, Germany, Colombia, India and Honduras.
Brazil has yet to legalise commercial use of agricultural biotechnology. However, its soybean farmers, who have watched their counterparts in the USA and Argentina enjoy the benefits of the technology, smuggle herbicide-tolerant biotech soybean seed from Argentina. They choose to do so despite the black market cost of seed, the availability only of varieties suited to Argentine growing conditions, and of course that growing such crops is not yet legal in Brazil. Production of these soybeans has reached such a scale that industry estimates put the figure as high as 70 per cent in the main soybean growing areas and the government was effectively forced to bring in an emergency decree in March 2003 to allow the sale of this aillegal' crop from this year's harvest.
There must be good reasons why farmers have adopted these new crops to such a large degree. Some of these are discussed in more detail below.
Quality improvements
In 2002, farmers in the American Midwest suffered the worst drought in decades. Agricultural productivity was reduced and water reservoirs severely depleted. Yet the position could have been much more serious had it not been for the uptake of herbicide-resistant biotech crops, which allowed the increased adoption of no-till farming.
Traditionally, growers would clear their previous crop and deep plough so as to hinder the re-growth of weeds. However, deep ploughing leaves fields exposed to wind and erosion. Biotech crops allow farmers to use no-till, by which a farmer plants the seed for a new crop directly into the soil through the residue of the previously harvested crop. The residue of the old crop eventually breaks down, thus adding valuable organic matter to the soil. Farmers now talk of the per centage of organic matter ainvested' in their soil almost as much as yields.
No-till not only minimises erosion, but it helps maintain the natural moisture in the soil so crops get a good start with less need for watering. This latter benefit is what came to the rescue of last year's drought-hit farmers. Thanks to nil or minimal tillage, soil erosion and movement are minimised, soil health and water retention ability is maximised. A study of conservation tillage by the American Soybean Association (ASA) found that three-quarters of growers who plant biotech varieties find that there is more crop residue on the soil surface using biotech varieties.
The avoidance of over-cultivation allows the natural fungi that grow on plant roots to produce glomalin, a protein that naturally sequesters carbon and keeps it within the soil. Glomalin helps to improve the fertility of soil by acting as a sort of aglue', causing soil particles to clump together properly. It creates subsurface spaces that allow water, oxygen, and plant roots to permeate the soil. The presence of glomalin is one of the main differences (apart from water) between fertile cropland soil and lifeless desert sand.
No-till is also energy saving because with just one operation seed drilling can be undertaken rather than conventional planting which needs three operations ploughing, harrowing, and drilling. Importantly, no-till helps reduce the levels of carbon dioxide and other pollutants formerly emitted by ploughing. The more that ahealthy' cropland soil is disturbed by mechanical cultivation, the more that the glomalin is broken-up and its (formerly sequestered) carbon allowed to re-enter the atmosphere in the form of the agreenhouse gas' carbon dioxide. Research published by Robertson et al. shows that farms, which use no-till methods, could reduce their greenhouse gas emissions by approximately 88 per cent compared with using conventional tillage.
Reduction in use of chemicals
Farmers control weeds either through mechanical cultivation or through the use of herbicides. Weed pressure will vary by location, but the corn and soybean farmers who use only mechanical cultivation may have to cultivate their fields as many as fourteen times per growing season. By contrast, the no-till and low-till methods use one and between two and four cultivation applications respectively, which can help to reduce soil erosion by 90 per cent or more.
Similarly, during average years of insect pest pressure, Bt. cotton yields per hectare have increased by approximately 7 per cent while the amount of chemical insecticides applied to Bt. cotton fields has decreased by approximately 50 per cent (ie 4.5 million litres during 1996-1999 in US).
Corn farmers who use insect resistant Bt. corn varieties have found that in years of average insect pest pressure, Bt. corn yields have increased by approximately 10 per cent, while US farmers have reported that they typically do not spray chemical insecticides at all on fields of Bt. corn. As such, if the sixteen largest corn-producing states in the USA were to convert 80 per cent of their corn hectares to Bt. varieties in years of average insect pest pressure, it would cut the use of chemical insecticides by 50000 tons a year. Similarly, soybean production shows at least a 10 per cent reduction in chemical use.
New proteins
Aside from operational benefits, glyphosate-tolerant soybeans contain an average of one-third fewer weed seeds and weed seed or plant particles when harvested. Some types of weed seeds could contain toxins and some might be allergenic.
As for concerns raised about anew' proteins introduced into biotechnology derived herbicide-tolerant soybean and canola varieties, those anew' proteins were originally discovered in several strains of common soil-dwelling bacteria: Agrobacterium tumefaciens for the glyphosate tolerant soybean and Streptomyces hygroscopicus and S. viridochromogenes for the glufosinate tolerant canola. Humans have breathed-in these bacteria for millennia on windy dusty days when field dirt was carried into the air.
contamination
Perhaps the greatest potential benefit to mankind offered by Bt. crops is reducing the risk of consuming harmful naturally occurring aflatoxin and other mycotoxins. These are toxins produced by fungi in insect-damaged corn and cotton. Due to tight controls and intensive testing developed over many decades, alfatoxins are usually well controlled in developed countries.
However, this is not true in the developing world. According to the United Nations Food & Agriculture Organization (FAO), 25 per cent of the world's food crops are affected with mycotoxins each year. That echoed a similar finding by Mannon and Johnson.
Most common of the mycotoxins is aflatoxin B1, one of the most heavily regulated compounds in foodstuffs. According to a 1993 World Bank report, aInvesting In Health', approximately 40 per cent of disability-adjusted life years lost to premature adult death in developing countries were due to diseases linked to consumption of mycotoxins.
Insects (eg, Pyralidae such as Ostrinia nubilalis) are the primary vectors for (carrying into crop plants) the Aspergillus flavus and A. parasiticus fungi that produce aflatoxin. These insects are best controlled by transgenic aBt. crops', which hold the potential to areduce or even eliminate mycotoxins in the food supply' due to elimination of insect damage to the crop.
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American Soybean Association is based in Brussels, Belgium. www.asa-europe.org
