Delayed-Flood Rice Production Research Articles

Tillage and Coated-Urea Effects on Nitrous Oxide Emissions from Direct-Seeded, Delayed-Flood Rice Production in Arkansas

Rice (Oryza sativa L.) is a key component of the diet of billions of humans, thus rice is a main agricultural product in many regions, particularly in eastern Arkansas, USA. Rice production is known to be a source of greenhouse gases, namely methane (CH4), but, under certain conditions, nitrous oxide (N2O) as well. The objective of this study was to evaluate the effects of tillage practice [conventional tillage (CT) and no-tillage (NT)] and urea fertilizer type [N-(n-butyl) thiophosphoric triamide (NBPT)-coated and non-coated urea] on N2O fluxes, season-long N2O emissions, and the global warming potential (GWP) from rice grown in eastern Arkansas in a direct-seeded, delayed-flood production system on a silt-loam soil.

Water Management and Cultivar Effects on Methane Emissions from Direct-seeded, Delayed-flood Rice Production in Arkansas

Methane (CH4) emissions from rice (Oryza sativa L.) production are a source of concern in the environmental and agricultural communities. New and/or revised agronomic methodologies will be needed to identify production practice combinations that reduced CH4 emissions without decreasing yields or milling quality. The objective of this study was to evaluate the effects of water management (i.e., full-season flood and mid-season drain) and cultivar (i.e., pure-line cultivar LaKast and the RiceTec hybrid XL753) on CH4 fluxes and season-long emissions from rice grown in the direct-seeded, delayed-flood production system on a silt-loam soil in east-central Arkansas.

Nitrogen Source Effects on Methane Emissions From Drill-Seeded, Delayed-Flood Rice Production

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) 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.

Diurnal Methane Fluxes as Affected by Cultivar from Direct-Seeded, Delayed-Flood Rice Production

Methane (CH4) emissions are known to differ between rice (Oryza sativa L.) cultivars, where CH4 emissions from pure-line cultivars are often greater than from hybrids. Numerous field studies have shown that CH4 emissions follow a diurnal pattern, typically reaching their maximum during afternoon hours. However, it is unknown whether cultivar affects CH4 fluxes/emissions at various measurement times of day or how those cultivar effects may differ spatially across soil textures and temporally throughout the rice growing season. The objective of this field study was to evaluate the effects of time of day (300, 800, 1200, 1800, and 2300 hours) and cultivar (one hybrid and one pure-line) on CH4 fluxes before and after heading from a silt-loam and clay soil in a direct-seeded, delayed-flood rice production system. Enclosed headspace chambers, 30 cm in diameter, were used for CH4 gas sampling on 22 July and 19 August at a silt-loam site and on 29 July and 26 August, 2014 at a clay-soil site in the Lower Mississippi River delta region of eastern Arkansas. Methane fluxes measured pre- and post-heading ranged from 0.7 to 2.2 mg CH4-C m-2· hr-1 from the clay soil and from 2 to 7 mg CH4-C m-2·hr-1 from the silt-loam soil. Hourly CH4 fluxes and estimated daily emissions differed among measurement times of day (P 4 flux or daily emissions for a given day differs by soil texture and rice growth stage, but conducting CH4 flux measurements around late morning to mid-day appear to be optimum to best capture the mean CH4 emissions for the day.

Cultivar and Previous Crop Effects on Methane Emissions From Drill-Seeded, Delayed-Flood Rice Production on a Silt-Loam Soil

Cultivar and Previous Crop Effects on Methane Emissions From Drill-Seeded, Delayed-Flood Rice Production on a Silt-Loam Soil

Cultivar and Previous Crop Effects on Methane Emissions From Drill-Seeded, Delayed-Flood Rice Production on a Silt-Loam 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 (184 kg CH4-C ha−1; 20.5 kg CH4-C (mg grain)−1). Hybrid rice emitted less (111 kg CH4-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 (186 kg CH4-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.

Soil Texture Effects on Methane Emissions From Direct-Seeded, Delayed-Flood Rice Production in Arkansas

AbstractRice (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 whic

Methane Emissions from Drill-Seeded, Delayed-Flood Rice Production on a Silt-Loam Soil in Arkansas

Rice ( L.) production is unique among staple food crops because the majority of the growing season typically occurs under flooded-soil conditions. Flooding the soil leads to anaerobic conditions, which are a precursor to methane (CH) production. However, no known research has investigated CH emissions from the drill-seeded, delayed-flood rice production system common in Arkansas, the leading rice-producing state in the United States. Therefore, research was conducted in 2011 to determine the effects of vegetation (rice and bare soil), chamber location (in- and between-rice rows), and nitrogen (N) fertilization (optimal and no N) on CH emissions from a silt-loam soil. Methane fluxes measured weekly from flooding until flood release were affected by vegetation, chamber location, and sample date ( < 0.05). In-row CH fluxes were <0.7 mg CH-C m h until 20 d after flooding (DAF) and <1.0 mg CH-C m h from between-row and bare soil until 41 DAF and were unaffected by fertilization over time. The largest weekly measured CH flux (31.9 mg CH-C m h) was observed from in-row rice at 41 DAF. Post-flood-release CH fluxes were affected by vegetation, fertilization, chamber placement, and sample date ( < 0.05) and accounted for approximately 3 to 7% of the season-long CH emissions. Methane emissions averaged 195 kg CH-C ha per growing season and were unaffected by fertilization. Direct measurement of CH emissions from drill-seeded, delayed-flood rice grown on a silt-loam soil will improve the accuracy of assessments of the carbon footprint and long-term sustainability of rice.

Predicting Nitrogen Fertilizer Needs for Rice in Arkansas Using Alkaline Hydrolyzable-Nitrogen

The immediate profitability and long-term sustainability of domestic crop production have been threatened by increasing N fertilizer costs. Currently, there is no soil test which can accurately predict the N fertilizer needs of direct-seeded, delayed-flood rice (Oryza sativa L.) produced on silt loam soils in Arkansas. Fertilizer N recommendations could be improved substantially with a calibrated soil N test, while also lowering potential environmental impacts. Twenty-five N response trials were conducted between 2004 and 2008 to correlate alkaline-hydrolyzable N (AH-N), as quantified by the Illinois Soil N Test (ISNT) and direct steam distillation (DSD), with rice response parameters such as total N (TN) uptake, check plot grain yield, and percentage of relative grain yield (RGY) and calibrate AH-N to predict the fertilizer N rate required to achieve 95% RGY. Relationships with the selected parameters were evaluated for both methods over a series of soil depth increments that included 0 to 15, 15 to 30, 30 to 45, 45 to 60, 0 to 30, 0 to 45, and 0 to 60 cm using linear regression models. Alkaline hydrolyzable-N was significantly and positively correlated with all rice response parameters except check plot grain yield and percentage of RGY using AH-N at the 45- to 60-cm depth. Coefficients of determination were greatest for percentage of RGY at the 0- to 30- and 0- to 45-cm depth for the ISNT (r2 = 0.57) and DSD (r2 = 0.73), respectively. Calibration of the fertilizer N rate to achieve 95% RGY resulted in similar trends as the correlation of rice response parameters, but with higher r2 values. Alkaline hydrolyzable-N explained 68 and 89% of the RGY variability in calibration for the ISNT using the 0- to 30-cm depth and the DSD using the 0- to 45-cm depth, respectively. These successful calibrations can be attributed to the N dynamics that exist in direct-seeded, delayed-flood rice production systems and identification of the proper sampling depth.

Evaluation of Polymer‐Coated Urea for Direct‐Seeded, Delayed‐Flood Rice Production

Rice (Oryza sativa L.) cultivated with the direct‐seeded, delayed‐flood production system relies heavily on post‐emergence aerial application of N. The availability of a controlled‐release N fertilizer suitable for preplant application would offer rice growers an alternative N‐fertilization method and reduce the aerial application costs of N fertilization. Our objectives were to determine grain yield and N uptake of rice receiving preplant incorporated polymer‐coated urea (PCU) compared with urea applied preflood at the five‐leaf stage and characterize the N release of two PCUs. Field trials were conducted at five site‐years to evaluate rice performance when fertilized with preplant‐applied Environmentally Smart Nitrogen (ESN) and Duration Type 5 (D5) and preflood‐applied urea across N rates ranging from 0 to 168 kg N ha−1 Nitrogen release from PCU was evaluated in field incubations using a buried‐bag method at two site‐years. Nitrogen release was nonlinear across time and similar between site‐years but different between PCUs. The nonlinear relationships predicted that 75% of PCU N content was released by 36 d for D5 and 25 d for ESN. Nitrogen recovery at panicle differentiation averaged 30% for D5, 26% for ESN, and 72% for urea and at heading averaged 47% for D5, 37% for ESN, and 101% for urea. As the N rate increased, yields increased nonlinearly for rice receiving D5 preplant and urea preflood and linearly for rice receiving ESN preplant. Yield predictions for D5 were always lower than for urea at the same N rates. Results suggest that the N release from D5 and ESN is too rapid for rice cultivated in the direct‐seeded, delayed‐flood method.