Objective:
1) Determine the fundamental relationships between spatiotemporal variation of corn and soybean yield and soil properties and processes; 2) Develop economical annual and perennial living groundcover management systems that conserve natural resources; 3) Evaluate cover crop and living mulch genotypes and species for corn-soybean agroecosystems in the Midwest that maintain main crop yields, increase soil organic matter, and reduce nitrate leaching; and 4) Assess the change in environmental quality and production risk associated with using cover crops in Midwestern cropping systems.

Approach:
Spatial patterns of corn and soybean grain yield will be collected from production fields within central Iowa each year. Several of these fields have extended spatial yield histories including one field with 14 years of observations. Data mining techniques including hierarchal, non-hierarchal, and fuzzy clustering, principal component analysis, discriminant analysis, and tree regression will be used to interpret annual yield patterns and to relate yield to soil and terrain attributes. Aircraft (hyperspectral) and satellite (broad-band) observations will be collected over a number of fields in Iowa in which tillage and nitrogen management practices will be imposed in large strips across the entire field. Reflectance will be measured for a variety of experiments with varying crop genetic, soil management, and nitrogen management strategies. These data will be used to develop and evaluate different vegetative indices (e.g., normalized difference vegetative index, near-infrared/red ratios, near-infrared/green ratio, nitrogen sufficiency index, soil adjusted vegetative index) for the detection of crop and soil responses to management practices. A corn soybean rotation will be examined with chisel plow, strip till, and no-till tillage systems. Results will be analyzed on a complete production system basis to evaluate the composite benefits and impacts of system on crop production and soil quality parameters. Cover crop management systems are not widely used in corn and soybean rotations in the upper Midwest because of cold temperatures during the winter and water limitations during the main crop season. Previous research or research in progress at this location has shown that cover crops reduce soil erosion and nitrate leaching in corn soybean rotations. Corn soybean cropping systems that include cover crops, however, often have reduced corn and soybean grain yields. A series of field experiments will be conducted to investigate the use of strip tillage, herbicides, mowing, and mechanical cultivation to restrict cover crops to interrow positions and to either kill or suppress cover crops before main crop planting.