From methane emissions to nitrate leaching, Big Agriculture is often vilified for practices contributing to rising greenhouse gas (GHG) emissions. But based on a large-scale historical analysis of land management practices, scientists now see farming as part of the climate change solution.
Using the DayCent ecosystem modeler on a 300-node computing cluster at Colorado State University, researchers combined comprehensive agricultural practices data with county-level historical soil and weather data from 12 Great Plains states from Texas to North Dakota. The US Environmental Protection Agency currently uses DayCent to do year-to-year soil carbon and nitrous oxide assessments.
“Our study is more than just a big data project,” says study author William Parton, senior research scientist at the Natural Resource Ecology Lab at Colorado State University. “These datasets are really a reflection of history in the Great Plains.”
Parton, who has a background in computer modeling, has been partnering for the last 15 years with agriculture historian Myron Gutmann, professor of history and director of the Institute of Behavioral Science at the University of Colorado, Boulder. Together, they offer the first complete big data perspective measuring cumulative GHG fluxes caused by all agricultural sources. Their results are published in the Proceedings of the National Academy of the Sciences.
The Great Plains region holds more than 30% of the US agricultural land area, producing more than 50% of winter wheat and more than 30% of beef production in the country. Parton and Gutmann divided 476 Great Plains counties into local regions to create 21 schedule files, and then interpolated them to the entire 12-state region. They then compared land management practices against 11,000 input variables, such as soil temperatures, tractor fuel consumption, irrigation energy efficiency ratios, and seasonal precipitation. This resulted in 477 datasets that now reside in a publically accessible database at the Inter-university Consortium for Political and Social Research.
Parton’s study shows that, spurred by shifts in technology and government policy, Great Plains farming practices went though many changes in the last 145 years. Cattle grazing supplanted the native bison and dominated Great Plains land management practice after the US Civil War. Accelerated by the Homestead Act of 1862 that gave land freely to those willing to cultivate it, a great plow-out followed until 1930. The third and ongoing wave of change came next when technological advances such as machines, fertilizers, pesticides, irrigation, and high yield crop hybrids remade the practice of farming. Cattle production has also increased during this last period.
This broad perspective yields valuable insights, and scientists now see that GHG flux is as much a product of change in land use as any particular farming practice. For example, a shift to irrigation and fertilizer application will enhance soil carbon storage, yet overall GHG emissions will increase through resulting nitrous oxide release.
This historical view also points to the potential for GHG mitigation. By implementing no-till or reduced tillage practices, adopting slow-release fertilizers, and inoculating cattle, Parton’s study predicts a 50% reduction in nitrous oxide emissions, 30% decrease in methane emissions, and an additional storage of 50 grams of carbon per meter per year. Farmers can measure their progress toward these goals through COMET-Farm, a free carbon and GHG accounting system Parton developed in partnership with the USDA's National Resources Conservation Service.
But practices that show promise in the Great Plains may not work in other regions, Parton is quick to point out. “Everywhere in the US we have sets of best management practices that could be implemented that have win-win effects where we should be able to reduce greenhouse gas emissions, reduce nitrate leaching, and not really hurt plant production — those are the kinds of things we are looking for.”
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