Nitrogen Release and Residue Persistence of Legume-Grass Cover Crop Mixtures in Reduced-Tillage Organic Corn Production.

No-till management is recognized for its potential to improve soil quality, reduce soil erosion and reduce machinery, labor and fuel costs; however organic production relies on intensive tillage as a primary weed control tactic. A cover crop-based rotational no-till corn system wherein fall-planted cover crops are rolled in the spring and the crop is no-till planted into the cover crop mulch may lend some of the benefits of no-till management to organic grain production. In such a system, cover crop selection is important because different species provide different services: legume cover crops release high levels of nitrogen (N) upon decomposition, which is needed for the high-N demanding corn crop, while grass cover crops produce a large amount of biomass for weed suppression. In this study, a range of hairy vetch (a legume, Vicia villosa Roth.) and triticale (a grass, x Triticosecale Wittmack) cover crop mixtures were tested across different modes of manure application to optimize corn N use efficiency and weed control. In 2011, cover crop biomass was greatest in the mixture planted at 40:60 vetch:triticale, but N content was greatest in the 80:20 and 100:0 vetch:triticale mixtures. Increasing proportion of vetch increased the rate of residue decomposition and total N release as measured in litter bags, but the effect of mixture proportion was reduced when poultry litter was pre-plant broadcast applied. Subsurface banded poultry litter applied at sidedress did not affect the decomposition rate of the residues relative to no poultry litter application. Residue decomposition was fastest in the standard tillage treatment, in which residues and poultry litter were incorporated prior to corn planting. Although optimum levels of biomass and N content were not achieved at the same cover crop mixture proportions, results suggest that subsurface banded poultry litter may provide supplemental N without affecting the persistence of the weed-suppressive mulch.