Rice (Oryza sativa L.) cultivation is unique compared with the production of most other upland row crops in that rice is typically produced under flooded-soil conditions, which can result in net emissions of methane (CH4). Nutrient applications for optimum production, specifically nitrogen (N), which can be organic or inorganic sources, are carefully managed in rice production. However, how nutrient-source effects on CH4 emissions from rice production may interact with other known factors affecting CH4 emissions, such as previous crop/crop rotation and soil texture, are poorly understood, particularly in the midsouthern United States where rice production is concentrated. The objective of this study was to evaluate CH4 fluxes and season-long emissions as affected by fertilizer-N source (i.e., ammonium sulfate [AS], pelletized poultry litter [PPL] + urea, and urea only) and previous crop in rotation (i.e., soybean [Glycine max L.] or rice) from rice production on a clayey Epiaquert and a silt-loam Albaqualf in the Lower Mississippi River Delta region of eastern Arkansas. Methane fluxes, measured using 30-cm-diameter, enclosed-headspace chambers, peaked near heading for all treatments, with PPL + urea resulting in greater (P < 0.05) peak fluxes than for the other fertilizer-N sources from both soil textures. Methane fluxes were consistently numerically lower from the clay soil throughout the growing season than from the silt-loam soil. Methane emissions from AS were, on average, 21% lower (P < 0.05) than from PPL + urea or urea only, which did not differ, from the silt-loam soil. Methane emissions were 60% lower (P < 0.05) when soybean was the previous crop compared with rice on the clay soil, but were unaffected (P > 0.05) by previous crop on the silt-loam soil. Results clearly indicate that the choice of fertilizer-N source for certain soil textures, specifically AS application to a silt-loam soil, has the potential to mitigate CH4 emissions and reduce the large, negatively perceived, C footprint associated with rice production.
1Department of Plant, Soil, and Entomological Sciences, University of Idaho Aberdeen Research and Extension Center, Aberdeen, ID.
2Department of Crop, Soil, and Environmental Sciences, University of Arkansas Fayetteville, AR.
Address for correspondence: Kristofor R. Brye, PhD, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, 115 Plant Sciences Bldg, Fayetteville, AR 72701. E-mail: firstname.lastname@example.org
Financial Disclosures/Conflicts of Interest: None reported.
Received September 8, 2016.
Accepted for publication December 3, 2016.