Legume Proportion, Poultry Litter, and Tillage Effects on Cover Crop Decomposition

Cover crop residues and animal waste products can be important sources of N in cropping systems. The objectives of this research were to determine, under field conditions, the effects of hairy vetch (legume; Vicia villosa Roth)/cereal rye (grass; Secale cereale L.) proportion and pelletized poultry litter (PPL) management (no PPL, subsurface banded, broadcast, or incorporated with tillage) on the extent and rate of cover crop residue mass loss and N release during a subsequent growing season. Measuring cover crop residues placed in mesh litter bags, or residues+PPL in litter bags for the broadcast treatment, we found that increasing hairy vetch proportion led to greater proportional mass loss and N release (cumulative mass loss ranged from 40 to 80% and N release ranged from 0-90% of initial), as well as greater rates of mass loss in all PPL treatments. Nitrogen release rates were generally unaffected by species proportions; however, N release rates for pure cereal rye residue in all PPL treatments except broadcast could not be estimated due to minimal N release. Incorporation of residues and PPL increased the rates of mass loss and N release for pure hairy vetch and hairy vetch-cereal rye mixtures. Although broadcast PPL application and incorporation affected decomposition patterns, subsurface banded PPL application did not. Results suggest that cereal rye provides the greatest mulch persistence, hairy vetch provides the greatest N release, and mixtures provide moderate delivery of these two services. Subsurface banding is the recommended