Nitrous Oxide Emissions from Subsurface Banded Poultry Litter in a Cover Crop-Based Corn System.

Nitrous oxide fluxes were monitored for three years in an experiment in Beltsville, MD, to investigate the effects of cover crop (cereal rye, hairy vetch, biculture, and absent), soil management (till vs. no-till), and fertility source, rate, and application timing. Cover crop termination and fertilization events were the major drivers in cumulative N₂O emissions. Cover crop presence increased cumulative N₂O production, with pure hairy vetch residue contributing more than the cereal rye or cereal rye-hairy vetch residues. In treatments with mineral fertilizer or tillage-incorporated poultry litter, more than half of the annual emissions occurred within 30 days of fertilizer application. In treatments with no-till subsurface banded poultry litter, fluxes continued to be substantial much later into the growing season. Within each cover crop, there was a linear relationship between cumulative emissions and fertilization rate. However, emission factor, the ratio of N₂O released to N applied, decreased with increasing rates of subsurface banded poultry litter. Emission factor did not differ between bare-ground, cereal rye, and cereal rye-hairy vetch cover crops, but was higher under hairy vetch residue.