Location: Agroecosystem Management Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop management strategies to optimize input use, e.g. water, nutrients, in cropping systems for grain and feedstock production. a. Compare production and water and nutrient budgets for annual grain and feedstock systems to those for perennial feedstock systems. b. Develop amelioration practices for cropping systems affected by residue removal. Objective 2: Identify and quantify ecosystem services in grain and feedstock production systems. a. Quantify carbon sequestration in annual grain and feedstock systems and perennial feedstock systems. b. Quantify leaching in irrigated and rainfed cropping systems. c. Quantify greenhouse gas emission from annual and perennial cropping systems. d. Compare diversity and activity of soil microorganisms among management systems. Objective 3: Develop management guidelines and protocols for managing spatially variable fields. a. Determine management zones for efficient use of inputs. b. Develop precision management tools to optimize input use efficiency. c. Utilize process models to manage spatially variable fields.
1b. Approach (from AD-416):
Increasing concerns about rising atmospheric concentrations of greenhouse gases (GHG) have emphasized the critical need for soil and crop management strategies that can mitigate GHG impacts while meeting societal demands for products (i.e. food, fiber, and fuel) and societal expectations of water and air quality. Soil and crop management strategies can optimize the capacity of agricultural soils to store carbon (C) while minimizing emissions of N-based GHGs by optimizing nitrogen (N) fertilizer applications across spatially variable landscapes. This project will (1) determine how crop and residue management affects soil functions (i.e. soil fertility, C storage and soil organic matter dynamics, GHG fluxes, and role of soil microbial communities on these functions), and (2) develop approaches to delineate spatially variable fields for more efficient application of water and fertilizer inputs. Crop residues are currently being harvested to co-feed with distillers grain in livestock operations and have been identified as available sources of cellulosic biomass for biofuel production. This project plan will determine the impact that corn stover removal has on soil function and develop recommendations for determining the amount of stover that can be diverted to other uses without impairing soil function. Results will be shared with producers, consultants, extension educators, state and federal regulatory agency personnel, and other scientists. Products resulting from this project plan will contribute to improved soil and crop management that will maintain or improve the sustainability of agroecosystem soil function.
3. Progress Report:
Biomass (grain and stover), greenhouse gas sampling, and associated soil/environmental measurements continue from three separate long-term field experiments evaluating the effects of residue management in both non-irrigated and irrigated systems. Data from these three residue management experiments will contribute to several manuscripts being drafted for a special issue of Bioenergy Research. This special issue will summarize research conducted as part of the SunGrant Initiative. The DayCent Model is being validated using measured greenhouse gas emissions in non-irrigated residue management experiment. This modeling evaluation is being conducted in collaboration with scientists at Colorado State University. Greenhouse gas sampling and associated soil/environmental measurements were collected from a long-term study evaluating the effects of crop rotation and tillage management on grain production and soil properties. All greenhouse gas, soil, and crop yield data has been entered into the REAP and GRACEnet database systems.
1. Carbon sequestration in perennial and no-tillage corn feedstock systems reduces greenhouse gas emissions. Grain and biomass yields and composition, root zone soil carbon changes, and production input data were obtained from a long-term corn and switchgrass field trial in the western Corn Belt USA. ARS scientists in Lincoln, NE determined that switchgrass, when managed under best management practices, produced similar ethanol yields as intensified no-tillage corn systems (grain and residue harvest) and soil carbon content increased in the root zone of both crops. These results demonstrate that when soil carbon sequestration is included in the assessment, current and potential biofuels systems can significantly lower greenhouse gas emissions.
2. Carbon additions alone are not sufficient to maintain soil organic carbon content. Carbon sources varying in solubility and quality were surface applied to soil and soil carbon content, aggregate size distribution, and wet aggregate stability were compared to soils supporting annual or perennial grass with and without residue removal. ARS scientists in Lincoln, NE determined that soil receiving readily available carbon or left bare lost particulate organic carbon content and that soil with plant residue on the surface or supporting annual or perennial plants gained total organic carbon content, maintained aggregate size, and increased wet aggregate stability. Protecting the soil against raindrop impact and reducing the intensity of wetting and drying cycles are additional functions that surface residue provides that contribute to soil carbon sequestration.
Wienhold, B.J., Varvel, G.E., Johnson, J.M., Wilhelm, W.W. 2013. Carbon source quality and placement effects on soil organic carbon status. BioEnergy Research. 6:786-796. Available: http://link.springer.com/content/pdf/10.1007%2Fs12155-013-9301-z.pdf.