COLUMBUS, Ohio – Increase no-till farming practices across the planet or face serious climate, soil quality and food production problems in the next 20 to 50 years. That warning from scientists appeared in the journal Science this week.
No-till farming helps soil retain carbon. Healthy topsoil contains carbon-enriched humus – decaying organic matter that provides nutrients to plants. Soils low in humus can't maintain the carbon-dependent nutrients essential to healthy crop production, resulting in the need to use more fertilizers.
A lack of carbon in soil may promote erosion, as topsoil and fertilizers are often washed or blown away from farm fields and into waterways, said Rattan Lal, the paper's lead author and the director of the carbon management and sequestration center at Ohio State University.
In no-till agriculture, farmers plant seeds without using a plow to turn the soil. Soil loses most of it carbon content during plowing, which releases carbon dioxide gas into the atmosphere. Increased levels of CO2 in the atmosphere have been associated with global climate change.
Traditional plowing, or tilling, turns over the top layer of soil. Farmers use it for, among other reasons, to get rid of weeds, make it easier to use fertilizers and pesticides and to plant crops. Tilling also enriches the soil as it hastens the decomposition of crop residue, weeds and other organic matter.
Still, the benefits of switching to no-till farming practices outweigh those of traditional planting.
Since the mechanization of agriculture began a few hundred years ago, scientists estimate that some 78 billion metric tons – more than 171 trillion pounds – of carbon once trapped in the soil have been lost to the atmosphere in the form of CO2.
Lal and his colleagues estimate that no-till farming is practiced on only 5 percent of all the world's cultivated cropland. Farmers in the United States use no-till methods on 37 percent of the nation's cropland, which results in saving an estimated 60 million metric tons of soil CO2 annually.
"If every farmer who grows crops in the United States would use no-till and adopt management practices such as crop rotation and planting cover crops, we could sequester about 300 million tons of soil carbon each year," said Lal, who is also a professor of soil science at Ohio State.
"Each year, 6 billion tons of carbon is released into the planet's atmosphere as fossil fuels are burned, and plants can absorb 20 times that amount in that period of time," he said. "The problem is that as organisms decompose and plants breathe, CO2 returns to the atmosphere. None of it accumulates in the soil."
Lal admits that full-scale no-till farming practices are a short-term fix, but it's one that will give researchers enough time to find alternatives to fossil fuels.
"There needs to be a global effort to adopt no-till farming practices soon. Governments need to mandate these practices or to provide financial incentives to farmers to adopt them," said Lal, adding no-till methods may reduce a farmer's annual crop yield by 5 to 10 percent, at least for the first few years.
It's also tough to ask farmers who lack the necessary financial resources to switch to no-till methods, especially in African and Asian countries where no-till levels are the lowest, Lal said.
"No-till isn't readily practiced in most of these areas due to the lack of available financial resources and government support," he said. "Farmers often lack the seeding equipment necessary to drill through crop residue. And many farmers use leftover residue from the previous year's crops for fuel or animal fodder. So the cultivated soil gets compacted or eroded by water and wind."
Topsoil is also a lucrative commodity – an acre of it can bring in $1,300 for a farmer in India, where the first few feet of soil are often removed for brick making.
"No-till farming isn't a substitute for finding alternatives to fossil fuels," Lal said.
"No-till is definitely a short-term fix, but it may buy us up to 50 years to find alternatives to fossil fuels. If we don't heed this warning, our planet may change drastically. There's no other choice."
Lal co-authored the paper with Michael Griffin, Jay Apt, Lester Lave and M. Granger Morgan, all with Carnegie Mellon University.
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