2013 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.
This is the final report for project 3625-21610-001-00D, terminating August 4, 2013. During the five years of the project, significant progress was made in developing management strategies for enhanced soil and water quality in Midwestern cropping systems. A rye winter cover crop was planted in a corn silage-soybean rotation and soil carbon, potential nitrogen (N) mineralization, and particulate organic matter were measured in the upper 10 cm of soil. Results showed that a rye cover crop can reduce the impact on soil quality of removal of corn stover as silage. Further, when rye cover crops were grown with corn silage, levels of potential N mineralization and particulate organic matter were greater than those in a corn silage system without a rye cover crop. These results indicate that a winter rye cover crop can help to maintain soil quality in rotations where corn shoot biomass is removed. 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. Results 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. Research 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 104 to 274 cubic meters of natural gas. In a separate study with corn grown as a bio-energy feedstock 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, we found that after two growing seasons, the growing crop had adequate levels of all nutrients. This suggests that fertilizer application rates, placement, and timing can be adjusted to meet the needs of 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 four of the five years the study was conducted. Significant progress was made in an experiment to evaluate carbon (C) sequestration, root-zone water quality, soil quality, and vegetable quality within three-year organic vegetable rotations. Tomatoes were transplanted and sweet corn planted in June 2012. A rye/hairy vetch cover crop was planted in September 2012, and collection of water samples from lysimeters began in April 2013. Analysis of soil, plant, and water samples is in progress. At a separate organic corn and soybean production site, tile water flow monitoring began in 2012. Soil carbon dioxide flux data collection began during the 2013 growing season. Analysis of soil and water samples is in progress.
Bio-energy cropping systems utilizing corn stover can be sustainable. Growing crops as a bio-energy feedstock has attracted the attention of many producers, especially in the Corn Belt states. The long-term effects of both increasing grain yields and removing stover on soil nutrient cycling, physical properties, and biological activity must be understood to ensure that corn yields meet both current and future demands. A five-year field study conducted by ARS scientists in Ames, Iowa, compared several corn biomass management systems, including both standard fertilizer management and a high plant population treatment with increased nitrogen, phosphorus, and potassium additions. By adjusting fertilizer application rates, placement, and timing for the two nutrient management scenarios, we were able to show that concentrations of all nutrients in the growing crop could be maintained at optimum levels. During four of the five years the study has been conducted, differences in plant populations and tillage intensity, application of biochar, and use of cover crops did not affect corn grain or stover yields, suggesting that long-term research is needed to determine the effects of these management practices. 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.
Oat and rye cover crops substantially reduce nitrate losses in drainage water.
Nitrate in freshwater streams in the Mississippi River basin contributes to hypoxia in the Gulf of Mexico and often needs to be removed by municipal water treatment plants for use as drinking water. Much of the nitrate in the Mississippi River comes from land used to produce corn and soybean, especially if it has been drained with subsurface drainage systems. Oat and rye cover crops can substantially reduce nitrate losses in drainage water. Cover crops grown between maturity and planting of corn and soybean is one approach for reducing losses of nitrate. During a five-year period, ARS scientists at Ames, Iowa, showed that a cereal rye winter cover crop reduced the concentration of nitrate in drainage water by 48%. An 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.
Cambardella, C.A., Hatfield, J.L. 2013. Carbon dynamics in agricultural systems. In: Brown, D.G., French, N.H.F., Reed, B.C., Robinson, D.T., editors. Soil Carbon Dynamics in Agricultural Systems. New York, NY: Cambridge University Press. p. 381-402.
Carr, P.M., Delate, K., Zhao, X., Cambardella, C.A., Carr, P.L., Heckman, J.R. 2012. Organic farming: Impacts on soil, food, and human health. In: Brevik, E.C., Burgess, L., editors. Soils and Human Health. New York, NY: Taylor & Francis. p. 241-254.
Tufekcioglu, M., Isenhart, T.M., Schultz, R.C., Bear, D.A., Kovar, J.L., Russell, J.R. 2012. Stream bank erosion as a source of sediment and phosphorus in grazed pastures of the Rathbun Lake Watershed in southern Iowa, USA. Journal of Soil and Water Conservation. 67(6):545-555.
Delate, K., Cambardella, C.A., Chase, C., Johanns, A., Turnbull, R. 2013. The long-term agroecological research (LTAR) experiment supports organic yields, soil quality, and economic performance in Iowa. Crop Management. DOI:10.1094/CM-2013-0429-02-RS.
Ontl, T.A., Hofmockel, K.S., Cambardella, C.A., Schulte, L.A., Kolka, R.K. 2013. Topographic and soil influences on root productivity of three bioenergy cropping systems. New Phytologist. 199(3):727-737. DOI:10.1111/nph.12302.