Manure and Inorganic Fertilizer Management Practices for Reducing Methane and Nitrous Oxide Emissions in Conservation Tillage Systems.

Conservation tillage and use of poultry litter (PL) as a fertilizer are widely being recommended for soil conservation, C sequestration, and environmentally sustainable animal waste disposal methods in the southeastern U.S. There is a need to develop and evaluate fertilizer management practices for reducing soil emissions of greenhouse gases under conservation tillage and their impact on agricultural contributions of greenhouse gases. We investigated methane (CH₄) and nitrous oxide (N₂O) fluxes in a soil receiving PL and ammonium nitrate (AN) fertilizers for corn (Zea mays L.) production in no-till (NT) and conventional tillage (CT) systems, using surface (SA), soil incorporation (SI), and subsurface band application (BA) methods, on a Decatur silt loam soil in north Alabama. Soil gas samples were collected using custom built static chambers and analyzed for CH₄ and N₂O gas concentrations for calculating soil gas fluxes. Net positive soil CH₄ fluxes of up to 4 µg m^-2 min^-1 were found in CT plots with soil incorporation of AN (CT-AN-SI) and in NT plots with surface application of PL (NT-PL-SA) from April 2008 to March 2009. The other treatments were net sinks of atmospheric CH₄. Plots under the NT-PL-BA treatment were highest sinks of CH₄, with a net of -11.2 µg m^-2 min^-1. Net positive N₂O fluxes up to 117 µg m^-2 min^-1 were observed in CT-AN-SI plots. Plots under NT-PL-BA, CT-0N, CT-PL-SA, and CT-PL-BA treatments were net sinks of N₂O. Our study shows that band application of PL in NT system was the best management practice for reducing soil CH₄ and N₂O emissions in a corn production system on the Decatur silt loam soil in north Alabama. Surface application of PL in the NT system and soil incorporation of AN in the CT system had the highest potential to increase agricultural contributions of CH₄ and N₂O greenhouse gases.