Persistence and Nutrient Release from Organic Mulches and Cover Crops.

Traditional organic vegetable production relies on tillage for weed control, but organic producers may adopt no-till if sufficient weed suppression can be achieved. A combination of high biomass cover crops with organic mulches may provide vegetable producers with multiple benefits, including improved weed control, but information on nutrient release from these residues is lacking. Information on the timely release of nutrients from organic residues will help producers make informed decisions regarding residue management, including adoption of conservation or conventional tillage. The objective of this study was to assess nutrient release rates and mass loss from organic residues (mimosa, lespedeza, straw, and soybean) under conventional and conservation tillage for fall crop production. The experiment used litterbag methodology and consisted of a 2x4 factorial split plot design with four replicates. Nitrogen (N), phosphorus (P), potassium (K), and carbon (C) release and mass loss rates are greater when residues are buried, with the exception of N and P loss from straw, likely due to its low initial concentration of these elements. More N is potentially available to spring crops from surface residues, which act as a slow release fertilizer, compared to incorporated residues.  Compared to buried residues, surface residues placed in the fall have 403-883 kg ha^-1 more C sequestered and 1-50 kg ha^-1 more N potentially available at spring planting. This study demonstrates that in situ cover crops and mulches may be utilized under conservation tillage for the enhancement of SOM and soil N status.