Location: Agroecosystems Management Research2009 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
During the first year of the project, progress was documented in all three objectives. In objective one, 13 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 two, plant species were identified that are candidates for the carbon (C) and nitrogen (N) cycling experiments. In objective three, field plots were established for the winter rye and corn silage experiment and deep and surface cores were collected for soil C. For the runoff modeling component of objective 3, initial work has focused on using RUSLE2 (Revised Universal Soil Loss Equation , version 2) rather than WEPP (Water Erosion Prediction Program). Preliminary model predictions have matched past erosion measurements on a relative basis between treatments. Energy exchange measurements were made over cover crops and bare soil in the spring of 2009 using a sensible heat balance approach to obtain water use values. These data provide a daily estimate of water use that is used to estimate soil water in the profile at the time of corn planting. These data and rainfall probabilities will be used to determine the risk associated with cover crop water use in the spring prior to summer annual crop establishment.
1. Living mulches managed as forages in an extended corn-soybean rotation. Combining annual and perennial plant species in multifunctional cropping systems is one approach to achieving enhanced ecosystem function. Concurrent management of multiple plant species, including one with an immediate cash value (commodity or staple) and typically a perennial(s), is often termed a living mulch cropping system. Managing forages as living mulches during row crop production requires suppressing the forages to produce economical crop yields. Researchers at the National Soil Tilth Laboratory used alfalfa, kura clover, and birdsfoot trefoil in simple and binary mixtures and reed canarygrass and orchardgrass in three-way mixtures in a corn-soybean-forage rotation. The forages were managed as perennial cover crops in corn and soybean and suppressed using a 10 inch glyphosate band over the row and harvested four times during the forage year. In the forage year, treatments containing alfalfa produced the highest yields. Three-way mixtures provided greater weed suppression in the interrow than simple or binary mixtures. Kura clover provided greater weed suppression than alfalfa in the interrow and birdsfoot trefoil did not persist. Reed canarygrass exhibited better stability than orchardgrass. Consequently, the best combination of species to use as living mulches during row crop production and to provide high forage yields and lower weed densities during the forage phase in this crop rotation includes alfalfa, kura clover, and reed canarygrass. Seeding an unadapted alfalfa in the spring of the forage year will supplement yield and suppress weeds in the former crop row. Producers using this type of system can diversify their cropping systems, obtain high forage yields, and eliminate the lower yields usually obtained during a perennial forage establishemt year.
Singer, J.W., Franzluebbers, A.J., Karlen, D.L. 2009. Grass-Based Farming Systems: Soil Conservation and Environmental Quality. In: Wedin, W.F., Fales, S., editors. Grasslands: Quietness and Strength for a New American Agriculture. Madison, WI: ASA. p. 121-136.