Spare the plow, save the soil. (Agriculture).
In no-till farming, soil is not disturbed between harvesting one crop and planting the next; seeds are planted in stubble or sod instead of plowed soil. The goal of no-till is to leave as much of the soil surface and ground cover undisturbed as possible to provide protection against erosion, reduce soil crusting, and increase the soil's organic content. "The number one way to keep soil from eroding," says Towery, "is to keep it covered, and no-till leaves the most residue."
In a presentation at the First International World Congress on Conservation Agriculture, held in October 2001, agronomist Roll Derpsch said the United States has the largest area of no-till in one country, with 21.1 million hectares (18% of total cropland). The Brazil-Argentina-Paraguay region comes in second with 27 million hectares (as many as 90% of Paraguay's mechanized farms use no-till methods). Asia recently moved into third place: since 1998 the adoption of no-till more than tripled to over 100,000 hectares in 2001. Scientists at the International Maize and Wheat Improvement Center speculate that no-till in Asia may exceed 300,000 hectares within the next year. The absolute numbers of acres involved may not be high, but the rate of adoption is remarkable, says Wayne Reeves, a lead scientist and research agronomist at the U.S. Department of Agriculture-Agricultural Research Service National Soil Dynamics Laboratory in Auburn, Alabama.
Reeves is especially concerned with the effects of plowing on releasing carbon dioxide. "Each [plow pass] oxidizes organic matter and results in the release of carbon dioxide, which contributes to global warming," says Reeves. "By not tilling, the carbon is instead used to increase organic matter levels [in the soil]." He cites research by soil scientists at the U.S. Environmental Protection Agency Environmental Research Laboratory in Corvallis, Oregon, first published in 1993 in the Soil Science Society of America Journal, which estimated that if 76% of U.S. cropland were converted to no-till by 2020, it would change U.S. agriculture from being a net emitter of carbon into the atmosphere (with 188-209 million metric tons of carbon lost to the atmosphere) to being a net sink for carbon (storing 131-306 million metric tons of carbon).
Members of the Rice-Wheat Consortium for Indo-Gangetic Plains in Pakistan, Nepal, and India have found that no-till shortens the turnaround time between rice and wheat planting, allowing farmers to plant wheat on time and obtain better yields. Farmers using no-till sow wheat in a single operation immediately after the rice harvest, planting the seed directly into rice stubble.
Farmers in these same countries are using as much as 30-50% less water for irrigation since 1998, according to the consortium and the International Maize and Wheat Improvement Center. These groups also indicate that farmers use less herbicides--no-till results in two-thirds to one-half fewer weeds than conventional tillage, which brings weed seeds to the soil surface. Farmers can also get seed in earlier, before the soil dries up and in time for crops to mature fully before harvesting begins.
Although the first no-till planting occurred in the United States in the mid-1970s, Peter Hobbs, the International Maize and Wheat Improvement Center representative for South Asia, says there wasn't much interest until the past decade, when farmers in many regions began witnessing dramatic declines in profitability. These were partly related to ecologic degradation associated with conventional technologies such as unbalanced use of fertilizers, delayed planting, and the overuse of plowing, but also due to increased input costs including fuel and low output prices.
"We have lots of cases where an innovative farmer who agreed to try no-till was ridiculed by his fellow farmers," says Hobbs. "In some cases a farmer would plow up his field rather than be embarrassed. However, most [farmers who use no-till] get excellent results, and then it is hard to stop the other farmers from trying."
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|Publication:||Environmental Health Perspectives|
|Date:||Feb 1, 2002|
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