Methane Emissions from a Silt-Loam Soil As Affected By Previous Crop and Fertilizer Nitrogen Source.

Research concerning methane (CH₄) emissions as affected by previous crop and fertilizer nitrogen (N) source from drill-seeded, delayed-flood rice (Oryza sativa L.) production in Arkansas is limited. A field study was conducted during the 2013 growing season on a silt-loam soil.  The objective of this study was to investigate the influence of previous crop [soybean (Glycine max L.) or rice] and fertilizer N source (ammonium sulfate, urea, and poultry litter + urea) on the semi-dwarf cultivar Cheniere. Fertilizer N sources were applied at a rate of 168 kg N ha^-1, and poultry litter (3.7% N) was applied at a rate of 2242 kg ha^-1 with additional urea applied to ensure equal N rates across all treatments. Chambers were used to collect headspace gas samples at 0, 20, 40, and 60 min intervals weekly after flood establishment and then every other day for 1 wk following flood release. Emissions during the 2013 growing season only differed among N sources (P = 0.01). Averaged across previous crop, seasonal emissions from ammonium sulfate (125 kg CH₄-C ha^-1) were less than that from either urea (151 kg CH₄-C ha^-1) or poultry litter (170 kg CH₄-C ha^-1), which did not differ. This study indicated that ammonium sulfate can potentially reduce CH₄ emissions in drill-seeded, delayed-flood rice produced on a silt-loam soil as compared to urea or poultry litter + urea. Additionally, the application of poultry litter, at the rate tested during the current study, did not result in significant differences in CH₄ emissions compared to urea. Research concerning N source, particularly the addition of poultry litter, will help determine sustainable fertilizer management strategies in relation to the carbon footprint of rice production.