Management Practice To Reduce Greenhouse Gases Under Dryland Malt Barley Production
At the final Brownbagger session at the USDA-ARS Northern Plains Agricultural Research Laboratory in Sidney on April 5, Upendra Sainju, soil scientist from the Laboratory, spoke about his study on greenhouse gas emissions in agriculture and how they are affected by various management practices. In particular, Sainju looked at emissions in dryland malt barley production from 2008 to 2011.
Sainju stated that 6 to 14 percent of the total man-made greenhouse gases are produced by agricultural practices. These gases include carbon dioxide, nitrous oxide, and methane. Nitrous oxide and methane are 314 and 25 times more powerful, respectively, as carbon dioxide in terms of their global warming potential. The concentration of these gases are affected by farm operations used for tillage, fertilization, planting, herbicide and pesticide applications, and harvest, soil carbon sequestration, type of crops grown, and soil and environmental conditions, such as temperature, water content, and precipitation. While farm operations, nitrogen fertilizer production and application, and soil greenhouse gas emissions are major sources of greenhouse gas emissions, soil carbon sequestration and the amount of crop residue returned to the soil act as “sinks,” meaning they trap carbon in the soil and thereby reduce carbon dioxide emissions.
In order to measure soil greenhouse gas emissions under malt barley and pea, Sainju installed static chambers made of PVC pipe around the plant. Gases were sampled from the chamber at different time intervals and their concentrations were measured using a gas chromatograph in the laboratory. Sainju compared greenhouse gas emissions under conventional and improved management practices that included conventional till and no-till with malt barley, pea, and fallow which were, in turn, fertilized with or without 70 lb N/acre. He also measured the soil carbon sequestration rate and grain and crop residue yields for four years. From these measurements, he calculated the global warming potential and greenhouse gas intensity of the various crops and agricultural practices after taking account of all sources and sinks of greenhouse gases.
His study showed that the traditional farming system with conventional tillage, fallow, and nitrogen fertilization increased net greenhouse gas emissions. Improved management practices, such as a no-till malt barley/pea rotation with nitrogen fertilization, produced the lowest amount of net greenhouse gases compared to other management practices due to increased soil carbon sequestration and reduced nitrogen fertilization rate, as pea residue contributed additional nitrogen to the soil. This system also produced better malt barley yield and quality (less than 13.5% protein concentration, greater than 80% plump kernel) than the traditional farming system. Since grain yield increased with increased nitrogen rate without affecting yield and quality in the no-till malt-barley rotation, Sainju wants to continue the experiment with further refined rates of nitrogen fertilization so that an appropriate nitrogen rate can be identified for this system. The result would provide area producers with a viable management option for reducing greenhouse gas emissions while maintaining or increasing dryland malt barley yield and quality.