The long-term profitability and sustainability of organic corn (Zea mays) production must include reliable weed and fertility management strategies that minimize production costs, conserve soil, and maximize nutrient use efficiency. This may be accomplished through integration of novel manure subsurface banding technologies with an optimal legume/grass cover crop mixture and supplemental high-residue cultivation. The specific goals of this graduate student project are to 1) determine C and N release and persistence of decomposing cover crop surface mulches that vary in grass:legume proportions; 2) evaluate the effect of poultry litter placement on soil N spatial and temporal availability; and 3) determine the cover crop combination and poultry litter placement that optimizes N availability and corn N use efficiency. These goals will be addressed by one replicated, multi-year field experiment at the USDA Beltsville Agricultural Research Center. Knowledge gained from this research will be shared with farmers and agricultural professionals through on-farm field days, webinars and participation in an organic grain production workshop.
Project objectives from proposal:
1. Cover crop residue decomposition
a. Characterize C and N dynamics over time in decomposing cover crop residues composed of a range of legume:grass proportions to determine the mixture that results in the longest-lasting cover for weed suppression.
b. Determine the effect of poultry litter application (0 v. 67 kg plant available N ha-1), poultry litter placement (broadcast v. subsurface banded) and tillage on the rate of residue decomposition and N release for residues of varying composition.
2. Soil N
a. Characterize the spatial distribution of soil N in subsurface banded and broadcast poultry litter treatments across a gradient of cover crop mixtures and over time.
b. Determine the effect of high-residue cultivation on N distribution in subsurface banded and broadcast poultry litter treatments.
3. Crop and weed N uptake
a. Determine the efficiency at which N is taken up and the relative sufficiency of N for corn growth in no-till plots receiving subsurface banded, broadcast and no poultry litter, as well as in tillage plots receiving broadcast poultry litter with varying cover crop proportions.