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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 maxL.] 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. [ABSTRACT FROM AUTHOR]

The article focuses on characterizing method of methane gas emission from the production of rice in clay soil in Arkansas which leads to global warming and presents field treatments established on the clay soil.

The effects of cultural practices on drill seeded delayed flood rice (Oryza sativa L.) production on methane (CH4) emissions are not well quantified. In Arkansas, rice is produced predominantly on loamy soils following soybean (Glycine max L.) as the previous crop, and hybrid rice has replaced a large percentage of pure line cultivars in the past decade. Therefore, research was conducted during the 2012 growing season to assess the effects of previous crop (rice or soybean) and cultivar (standard stature, semi dwarf, and hybrid) on CH4 emissions on a silt-loam soil. A 30 cm diameter chamber based method was used to determine fluxes during the 2012 growing season. When soybean was the previous crop, fluxes were generally lower (P < 0.05) until heading, after which all fluxes decreased until flood release. Seasonal emissions differed based on previous crop and cultivar (P < 0.05). Area and yield scaled growing season emissions from rice following soybean were less (127 kg CH4-C ha-1; 13.7 kg CH4-C (mg grain)-1) than when rice followed rice(184kgCH4-C ha-1;20.5kgCH4-C(mggrain)-1).Hybridriceemitted less(111 kgCH4-C ha-1; 11.1 kg CH4-C(mg grain)-1) than semi dwarf (169 CH4-C ha-1; 18.3 kg CH4-C (mg grain)-1) or standard-stature rice (186kgCH4-C ha-1;21.9 kg CH4-C (mg grain)-1), which did not differ. Thus, results indicated decreased emissions when soybean was the previous crop and when the hybrid cultivar was grown. The incorporation of factors known to influence CH4 emissions (i.e., previous crop, cultivar, and yield) will improve estimates of the carbon footprint of rice. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is a semiaquatic plant produced globally as a staple food crop under flooded-soil conditions for the majority of the time it is actively growing. Prolonged flooding results in the rapid depletion of oxygen and renders the soil highly anaerobic and reduced, both of which are precursor conditions for methane (CH4) production. Thus, rice production is unique among agricultural crops in its susceptibility to atmospheric CH4 emissions. Among the numerous soil, plant, and agronomic factors known to affect CH4 fluxes and emissions, few direct, replicated, plot-scale comparisons among soil textures have been conducted and little direct in situ quantification has been conducted in the production system common to Arkansas, the top rice-producing state in the United States. Therefore, a study was conducted in the Mississippi River Delta region of eastern Arkansas during 2012 to evaluate the effect of soil texture (i.e., silt loam and clay) on weekly CH4 fluxes and seasonal emissions from the direct-seeded, delayed-flood rice production system common to Arkansas. Chamber-based enclosures, 30 cm in diameter, were capped; gas samples were extracted with a syringe at 0, 20, 40, and 60 mm; and samples were analyzed by gas chromatography. Results showed that significant CR4 fluxes began sooner (P < 0.05), increased more rapidly (P < 0.05), and achieved a significantly greater peak flux earlier (P < 0.05) from the optimally N-fertilized rice grown on the silt-loam than that on the clay soil. Seasonal emissions from N- fertilized rice produced on the silt-loam soil averaged 159.6 kg CH4-C ha-1, which was the same as the EPA-estimated 160 kg CH4-C ha-1 season-1 from primaxy-crop rice production. However, clay soil sea- sonal emissions from N-fertilized rice were less than 23% (P < 0.05; 35.6 kg CH4-C ha-1) that of silt-loam emissions using the same produc- tion system, rice cultivar, and N fertilization scheme. These significant soil textural effects on CH4 emissions clearly demonstrate that additional research is needed to better quantify the other known factors affecting CH4 emissions, particularly soil texture, before widespread regulation and policies are set that could have inappropriate, widespread, negative consequences on US rice production. [ABSTRACT FROM AUTHOR]