Cover Crop Enhances the Benefit of Fall-Applied Poultry Litter As Cotton Fertilizer.

The effectiveness of poultry litter as cotton fertilizer in regions with warm fall or winter months is reduced if applied in the fall or winter.  A 3-yr study was conducted in northern Mississippi to test whether litter applied in the fall can be as effective as litter applied in the spring for no-till cotton if applied in narrow subsurface bands with winter cover crop. The study compared ≈5.6 Mg/ha poultry litter applied in the fall vs. spring, in subsurface bands vs. broadcast, with winter cover crop vs. no cover crop as a 2×2×2 factorial treatment structure.  These treatment combinations were compared against an unfertilized control and a local standard fertilized with conventional inorganic fertilizers.  The results showed that planting wheat as a winter cover crop increased cotton lint yield by about 10% over no cover crop in all treatments including the unfertilized control, confirming the benefits of cover crop as an important conservation practice for no-till cotton.  In the first year, wheat cover crop increased lint yield by >15% relative to no cover crop if the litter was applied in the fall, suggesting that wheat cover crop conserved soluble nutrients from loss.  Similar indication of cover crop benefits were observed in the second year but not in the third year. The results also showed that litter nutrients are conserved better if applied in subsurface bands than by surface broadcast regardless of the presence of cover crop.  Fall-applied litter was as effective as spring-applied litter for lint yield if applied in subsurface bands but not if applied as surface broadcast.  The results suggest that fall-applied poultry litter may be as effective as spring-applied litter if applied in subsurface bands and this effectiveness may be enhanced by including winter cover crop.