The agricultural sector is responsible for 9 percent of greenhouse gas emissions in the U.S. and methane from the raising of livestock represents almost one-third of these emissions, according to the U.S. Environmental Protection Agency.
But researchers at Colorado State University’s Natural Resources Ecology Lab have developed best management practices that, if implemented, could result in a net zero greenhouse gas emission rate from agriculture in the Great Plains alone, with hopes to study other regions as well.
Senior research scientist Bill Parton and his team used agricultural census data from 1870 until 2000 to historically map the release of greenhouse gases in the Great Plains through agricultural practices. The census data, recorded on the county level for over 420 counties from Texas to North Dakota, provides information such as the number of animals, number of acres and crop yields among other categories.
The CSU team input the census data into a computer model which simulated soil carbon levels and greenhouse gas emissions, and how they changed over time, for more than a century. “The beauty of this is that we don’t need new research to know about the kind of things we can do better,” Parton says about the study.
It focuses on three major greenhouse gases: carbon dioxide released from plowing the soil and the later burning of fossil fuels from tractors and other machinery; nitrous oxide released from fertilizer; and methane released from animals, specifically range cattle.
The results of the study show that more than 80 percent of the greenhouse gases were emitted during the period of soil plow out, which peaked in the 1930s. Turning the prairies of the Great Plains into crop-producing fields releases half of the carbon that naturally occurs in the soil into the atmosphere, or a 50 percent carbon loss in the soil. “Then we actually started to use better management practices, with tractors we didn’t plow the soil as often or disturb it as much,” Parton says.
However, the new machinery, by the burning of fossil fuels, added new sources of greenhouse gases and increased emissions. After the ’30s, farmers also started using fertilizer, the production of which burns natural gas and coal. And adding fertilizer increased the nitrous oxide emissions as well.
Plus, according to the census data, the number of beef cattle increased 120 percent form 1935 to 1970 alone, and it has continued to increase ever since, mainly driven by the meat industry. This has only added to greenhouse gas emissions in the form of methane.
But using this data allowed Parton and the team to also study best management practices to reduce emissions from the agriculture sector. “We know what we’re doing and we know how much better we can be,” Parton says.
These practices don’t actually suggest reducing the use of tractors, the production of fertilizer or number of animals in the agricultural sector but rather they create a system so that the greenhouse gases are recaptured in the soil to offset the emissions released in the atmosphere, Parton explains.
“The losses of greenhouse gases from producing fertilizer, the tractors and the cattle could be completely eliminated by storing carbon in the soil, for example using no-till,” he says. “Over 60 percent of potential benefit the way we calculated it comes from this no-till.”
No-till is an agricultural technique that doesn’t disturb the soil year to year but rather leaves the old plant residue on the surface of the field, which actually increases water retention and nutrients. The downside is no-till has the potential to create more weeds which then require the spraying of herbicides.
The study also suggests using slow-release fertilizers, which reduces the amount of fertilizer farmers need to apply, therefore reducing the nitrous oxide emissions. Other possibile management practices are altering feed and using injections to reduce methane released from cattle and other animals. However, these can be difficult to implement and aren’t cost effective for the farmers without significant subsidies.
Parton estimates a 24 percent reduction of greenhouse gas emissions if only 25 percent of farmers in the Great Plains adopt these best management practices. A 75 percent increase in adoption rates could result in a 102 percent reduction in emissions.
Given that less than 5 percent of the greenhouse gases from agricultural practices are from the Great Plains, still more research is needed to significantly reduce emissions from the agriculture sector nationwide. But Parton is hoping the CSU study is replicated in other regions throughout the country in order to determine best management practices that will reduce greenhouse gas emissions from the agricultural sector all together. “In the Great Plains this is the unique set of things we can do here,” he concludes. “The bigger picture is that all of agriculture could substantially reduce greenhouse gases if they use their best management practices.”