Farmers may be able to lower the net rate of the “greenhouse gases” — known as the “global warming potential” — that their farming systems emit, according to Agricultural Research Service scientists and university collaborators.
The scientists found that certain activities, such as switching to no-till farming, may also increase crop yields while helping the environment.
Some gases in the atmosphere trap heat near the Earth's surface, much like glass panes trap heat inside a greenhouse. Agricultural systems both release and absorb certain greenhouse gases. The difference between the total emission and absorption of these gases helps researchers understand the global warming potential.
Plants remove carbon dioxide, an important greenhouse gas, from the air and convert it to carbon-containing compounds. Eventually, much of that carbon returns to the soil as crop debris or waste from animals that ate the plants.
Carbon improves soil
Carbon that stays in the soil improves soil conditions for agriculture and also “sequesters” the gas out of the atmosphere. But crop and animal residues in and on the soil are decomposed by microbes, releasing the carbon dioxide back into the air.
Nitrogen fertilizers can be converted by microbes to nitrous oxide, a potent greenhouse gas. A third greenhouse gas, methane, can be released or absorbed by soils and is also released by some kinds of livestock and animal wastes.
Fort Collins, Colo., is one ARS location studying global warming potential. There, chemist Arvin R. Mosier and soil scientist Ardell D. Halvorson, of the ARS Soil, Plant and Nutrient Research Unit, and Gary A. Peterson of Colorado State University believe that switching to no-till farming, a system of cultivation in which the soil is not disturbed, will decrease the global warming potential on some farms. Soil disturbance stimulates much of the microbial activity that converts organic matter and nitrogen fertilizer into the greenhouse gases.
Around the country, ARS scientists are studying how a wide variety of management practices affect the global warming potential.