Developing Nitrogen Credits for Fall-Applied Poultry Litter and Winter Cover Crops in Corn Production.

Minimal N credits for fall-applied poultry litter are assigned for corn (Zea mays L.) based on current knowledge.  The objective of this study was to optimize the use of fall-applied poultry litter (PL) as an organic-based fertilizer coupled with winter cover crops for soil nutrient management in corn production.  The study was arranged as a randomized complete block with 12 treatments and 4 replicates conducted at Mississippi State, MS.  Treatments included PL applied at a rate of 2 mT ha^-1  and N equal to 71 kg ha^-1., and PL with cover crop treatments of rye, (Secale cereal L.), a legume mixture of crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth), and a combination of rye and legume mix.  All cover crop treatments were also grown without PL.  Five fertilizer N treatments at rates of 0, 56, 112, 168, and 224 kg N ha^-1 were included to provide an N index for comparing benefits of the PL-cover crop treatments.  Rye with PL produced the greatest amount of dry biomass and both the legume and legume with PL were significantly lower than any other cover crop treatment, but not significantly different from each other.  Treatment effects of the fall applied PL and cover crop combinations on corn leaf N at tasseling were significant.  The legume-rye-PL treatment resulted in significantly higher corn leaf N content than legume-PL treatment, legume without PL treatment, and the PL without cover crop treatment.  Based on the corn leaf N, Legume-rye-PL had a preliminary N fertilizer equivalent of 98 kg of N ha^-1.  The rye-PL treatment resulted in significantly greater leaf N than the PL alone expressing a preliminary N equivalent of 82 kg N ha^-1.  Rye alone resulted in significantly higher corn leaf N than the zero nitrogen treatment and was equivalent to 52 kg N ha^-1.  These results suggest that fall applied poultry litter coupled with the fixing and scavenging properties of legume and rye cover crops can improve the N credit to a spring corn crop.  Final N equivalency will be based on corn yield and grain N content.