Location: Agroecosystems Management Research2010 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
The second year of the project coincided with a laboratory reorganization. Consequently, nine research projects were merged into five. During the reorganization, some work on specific objectives was delayed or terminated. Nevertheless, progress was documented in all four objectives of the reorganized project. In Objective 1, winter small grain cultivars were planted and spring cover crop shoot dry weight, corn harvest plant populations, and yield data were collected. All data were collected in the perennial groundcover experiment and the data are being analyzed. In Objective 2, plant species were identified that will be used for the carbon and nitrogen cycling experiments. In Objective 3, field plots were established for the winter rye and corn silage experiment and surface cores were collected for soil carbon, potentially mineralizable nitrogen, and particulate organic matter. In Objective 4, soil fertility data are being collected in the large biomass study in Field 70/71 at the Agronomy Farm. Additionally, tile should be installed in the organic research plots this summer and the plots should be ready to initiate the rotations next year.
1. Enhancing Manure Nitrogen Retention with Cover Crops. Swine manure applied to agricultural fields is an important source of plant nutrients and organic matter. The most commonly used manure management practice in the Midwest involves fall application of liquid swine manure to land where corn will be grown in the subsequent growing season. Fall planted winter annual cover crops can capture manure nitrogen and release it the following spring, helping to synchronize manure nitrogen availabilty with corn nitrogen uptake. ARS researchers in Ames, Iowa, conducted experiments to evaluate the effects of integrating a rye/oat cover crop with liquid swine manure injection on retention of manure nitrogen in a corn-soybean cropping system, and found that a fall planted rye/oat cover crop reduced soil inorganic nitrogen after liquid swine manure injection. Cover crop effects on soil nitrogen were observed within a month after application and persisted into the following spring. These results quantify the potential for cover crops to enhance manure nitrogen retention and reduce nitrogen leaching potential. The information is useful to researchers and producers and will impact nutrient management decisions in farming systems that utilize manure.
2. Enhancing Soil Carbon with Cover Crops. Winter cover crops have the potential to sequester or maintain soil carbon in Midwest cropping systems. Maintaining soil carbon and soil productivity is especially important in cropping systems where most of the plant residues are harvested, such as in corn silage production or biofuel production. ARS researchers in Ames, Iowa, planted rye winter cover crops in a corn silage-soybean rotation and measured soil carbon in the upper 10 cm of soil after five years. Soil carbon was maintained relative to a corn grain-soybean rotation without silage removal when a rye cover crop was grown after both corn silage and soybean. However, without the cover crops soil carbon decreased by 6% for a corn silage-soybean rotation relative to corn grain-soybean rotation. This result is important because it shows that cover crops can sequester soil carbon in Midwest cropping systems and that corn stover can be harvested for animal feed or biomass without depleting soil carbon or soil productivity if winter cover crops are successfully managed.
3. Minimizing Phosphorus Losses with Cover Crops. Injection of liquid swine manure disturbs surface soil, so that runoff from treated lands can transport sediment and nutrients to surface waters. With a field study, ARS researchers in Ames, Iowa, determined the effect of two swine manure application methods on phosphorus fate in a corn-soybean production system, with and without a winter rye/oat cover crop. Manure application increased available soil phosphorus in the 20-30 cm layer following knife injection, while the highest phosphorus levels were detected in the 5-20 cm layer following low-disturbance injection. The low-disturbance system caused less damage to the cover crop, so that plant growth and phosphorus uptake were more than three-fold greater. Losses of dissolved phosphorus were greater in both the fall and spring following low-disturbance injection; however, application method had no effect on total phosphorus lost in runoff in either season. Low-disturbance injection of swine manure into a standing cover crop can minimize both damage to the cover and losses of phosphorus to surface runoff, while providing optimum phosphorus availability to corn. The results of this work will contribute useful information to swine producers and Cooperative Extension and NRCS personnel interested in alternative management practices that improve water quality.
4. Sulfur Management in Corn for Grain and Biomass. Sulfur is an essential plant nutrient that must be available to corn roots in order to achieve optimum growth. Our understanding of the effects of removing both corn grain and stover as potential biofuel feedstocks on soil sulfur supplies is limited. With a field study, ARS researchers in Ames, Iowa, evaluated the performance of several sulfur fertilizers for corn. After three years, they found that an application of 30 lb sulfur per acre increased early-season growth and plant sulfur concentrations and increased grain yield. These results suggest sulfur may quickly become a limiting nutrient for corn grown to supply biofuel feedstocks. The results of this research will benefit both commercial growers and the fertilizer and ethanol industries by providing nutrient management guidelines that maximize crop utilization and biomass yields.
Hatfield, J.L., Prueger, J.H. 2010. Value of Using Different Vegetative Indices to Quantify Agricultural Crop Characteristics at Different Growth Stages under Varying Management Practices. Remote Sensing. 2:562-578.