Location: Agroecosystem Management Research2012 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:
Both short term and long-term projects are being used to accomplish project objectives. Comparison of management strategies in long-term studies as well as new studies designed to address new and developing management options, are being utilized to make these assessments. Greenhouse gas samples, in-season water use measurements, plant canopy measurements, grain yield and total biomass, and soil samples are being collected from each study to make these assessments. Specifically, yearlong greenhouse gas and fall-collected soil samples from two of the long-term studies are being processed and analyzed. Soil organic carbon levels were shown to have increased throughout the profile in these two different management scenarios, but the mechanisms for this are not yet determined. The results strongly suggest that soil organic carbon sequestered at these depths would be less likely to be lost if the soil was tilled. Expanded efforts in these and other studies investigating residue removal on soil organic carbon sequestration should lead to a greater understanding of the soil processes and how they are being affected by the various management scenarios.
1. Net benefits of bioenergy crops including maize and perennial grasses such as switchgrass, are a function of several factors including the soil organic carbon (SOC) sequestered by these crops. In the first nine years of a long term carbon sequestration study in eastern Nebraska USA, ARS researchers from Lincoln, NE and Fort Collins, CO determined that switchgrass and maize had average annual increases in SOC content when the crops were grown under best management practices. For both switchgrass and maize, over 50% of the increase in SOC was below the 30 cm soil depth. In addition, nitrogen fertilization rates and harvest management regimes affected the magnitude of SOC sequestration. The study indicates that many commonly held assumptions regarding soil carbon sequestration, especially for cellulosic bioenergy crops, are questionable.
Wienhold, B.J. 2012. Cob component of corn residue can be used as a biofuel feedstock with little impact on soil and water conservation. Natural Resources Research Update (NRRU). Update #278169. Available at: http://hdl.handle.net/10113/44286, http://hdle.handle.net/10113/48120.