Location: Agroecosystems Management Research2012 Annual Report
1a. Objectives (from AD-416):
Overall objective: To develop and transfer technologies to manage Midwestern cropping systems which enhance soil and water quality and maintain profitability. Objective 1: Develop strategies for incorporating annual and perennial cover crops into continuous corn and corn-soybean management systems. Objective 2: Quantify changes in C and N cycling resulting from inclusion of cover crops within corn-soybean based cropping systems. Objective 3: Assess erosion and soil quality impacts and production risk associated with using cover crops, complex rotations, and bioenergy production in Midwestern cropping systems.
1b. Approach (from AD-416):
A combination of controlled environment, plot, and watershed-scale studies will quantify functional components of cover crops to develop enhanced Midwestern cropping systems. Up to fifteen winter rye, triticale, and wheat cultivars will be obtained from commercial sources and planted with a grain drill following soybean harvest. Results will quantify corn grain yield response to cultivars of winter rye, wheat, and triticale used as winter cover crops in a corn-soybean rotation. Perennial cover crop research using various herbicide and strip tillage management systems in continuous corn with stover removal will quantify C inputs from cover crops and their effect on corn yield. Inter-species differences in plant growth parameters may affect a cover crop’s potential to sequester soil C. Research will quantify total aboveground and belowground C and N allocation, rhizosphere respiration, and net mineralized N for selected cover crops grown under controlled conditions, quantify changes in surface residue, root, and soil C and N pools and cumulative net mineralized N and respired C during decomposition of cover crop biomass under controlled conditions, and field experiments to quantify the effects of the cover crop on soil C cycling and storage within extended corn-soybean based crop rotations with and without compost amendment. Field studies will evaluate the impact of corn stover removal with and without rye and perennial cover crops on soil quality. A modeling study will evaluate the effect of a winter rye cover crop on soil erosion in corn-soybean rotations using georeferenced terrain and cropping system data from two western Iowa watersheds. Evaluation of risk to crop yield induced by the removal of soil water by cover crops will be assessed with a combination of simulation models and experimental observations. Simulation results will be obtained with the Precision Agricultural-Landscape Modeling System (PALMS) model. The simulation model allows for an extension of the results to different soil types and climates and will be used to assess the degree of risk imposed on the main crop through soil water removal patterns.
3. Progress Report:
Significant progress has been made in addressing Objective 1. Data collection has been completed, and a research paper is being prepared (Objective 1.1). To address Objective 1.2, a fourth year of data was collected, and results indicate that corn growing in a Kentucky bluegrass living mulch with paraquat and glyphosate herbicide suppression and fall strip-till yields similarly to a control without a living mulch. A field study was continued to identify carbon (C) and nitrogen (N) partitioning of annual medics in different proportions with oat in order to quantify how much nitrogen the cover crops provide to a subsequent corn crop (Objective 2). Significant progress has also been made in addressing Objective 3. Analysis of samples from last year is complete for Objective 3.1. Two years of data indicate that potential nitrogen mineralization and particulate organic matter levels are greater when rye cover crops are grown with silage corn than when silage corn is grown without a rye cover crop. This indicates that a winter rye cover crop can help maintain soil quality in rotations where corn shoot biomass is removed. Work on Objective 3.3 is progressing with data set assembly and model runs planned for summer and fall 2012. An experiment to evaluate effects of no-tillage, cover crops, compost amendment, and mulch within three-year organic vegetable rotations on C sequestration, root-zone water quality, soil quality, and vegetable quality continued. A rye/hairy vetch cover crop was planted in October 2011, and collection of water samples from lysimeters began in April 2012. Peppers were transplanted and sweet corn planted in June 2012. Analysis of soil, plant, and water samples is in progress. In a separate study, a fourth year of data was summarized for corn grown as a bio-energy feedstock in a field trial under a variety of management systems, including 30-inch row spacing with standard fertility management and a twin-row, high-population treatment with increased nutrient additions. Analysis of whole plants at V6 and ear leaves at mid-silk showed adequate levels of all macronutrients, which suggests that nutrient management was balanced for the two planting scenarios and the amount of stover removed from the field. Management scenario, tillage, and previous stover removal did not affect corn grain yields in 2011. At the Iowa State University Agronomy Farm organic water quality site, tile water flow monitoring began in December 2011. Compost was applied to organic corn and oat plots, and organic oats seeded in March, 2012. Organic alfalfa and pasture plots were seeded in April, and corn and soybeans were planted in organic and conventional plots in May. Nitrogen fertilizer and herbicide were applied to conventional plots in June. Oat grain was harvested on July 2, 2012, and oat straw was raked and baled. Analysis of soil and water samples is in progress.
1. Oat and rye cover crops substantially reduce nitrate losses in drainage water. Much of the nitrate in the Mississippi River comes from land used to produce corn and soybean. Cover crops grown between maturity and planting of these crops are one approach for reducing losses of nitrate. ARS scientists in Ames, Iowa, showed that a rye winter cover crop reduced the concentration of nitrate in drainage water by 48% over five years. The oat fall cover crop reduced nitrate concentrations by 26%. Both oat and rye cover crops are viable management options for reducing nitrate losses to the Mississippi River from land used for corn and soybean production.
2. Sustainable bioenergy cropping systems using corn stover. Growing crops as a bio-energy feedstock has attracted the attention of many producers; especially, in the Corn Belt states. In a field study with a variety of management systems, including both standard fertilizer management and a high-population treatment with increased nutrient additions, ARS scientists in Ames, Iowa, found adequate levels of all nutrients in the growing crop, suggesting that current fertilizer application rates, placement, and timing were sufficient for the two management scenarios. Differences in plant populations and tillage intensity, application of biochar, and use of cover crops did not affect corn grain or stover yields during three of the four years the study has been conducted. The results of this research are providing nutrient management guidelines that maximize crop utilization and biomass yields, and will benefit commercial growers, as well as the fertilizer and ethanol industries.
3. Alternative nitrogen (N) fertility strategies can reduce environmental risks associated with corn production. Production of synthetic N fertilizer requires large quantities of fossil fuel energy and soil application of synthetic N fertilizer for corn production results in nitrate contamination of surface and groundwater resources. Adopting alternative strategies for supplying N to corn that rely on ecological processes rather than industrial processes may help reduce the environmental risks associated with corn production. ARS scientists, in Ames, Iowa, working in collaboration with university researchers, demonstrated that corn plants accumulated 23% more N after application of composted manure compared to fresh manure even though seasonal patterns of N mineralization and inorganic N were similar for composted and fresh manure. The collaboration also demonstrated that intercropping red clover or alfalfa with oats to supply N for corn production resulted in a fossil fuel energy savings equivalent to the energy content of 1487 to 3917 cubic feet of natural gas per acre. Alternative strategies are likely to become more important as fossil fuel energy supplies become scarcer and fertilizer prices rise. This information will be useful to scientists, farmers, and public and private organizations who are interested in economically viable ecologically-based N fertility strategies for corn production.Wiggans, D.R., Singer, J.W., Moore, K.J., Lamkey, K.R. 2011. Maize water use in living mulch systems with stover removal. Crop Science. 52:327-338.