See more from this Session: S4-S8 Graduate Student Poster Competition
Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
Rice (Oryza sativa L.) is the only staple crop grown under flooded soil conditions. Flooded soil conditions markedly impact the soil through depletion of oxygen (O2) and subsequent reduction of chemical compounds. The reduction of chemical compounds results in the release of greenhouse gases to the atmosphere. Of primary concern are nitrous oxide (N2O) and methane (CH4), which are released when nitrate (NO3-) and carbon dioxide (CO2) are utilized as terminal electron acceptors. A greenhouse study was initiated to investigate changes in soil redox potential in Arkansas paddy soils and to measure water column parameters with and without rice present. DeWitt silt loam and Calloway silt loam soils were collected from the plow layer of a rice/soybean (Glycine max L.) rotation from the Rice Research and Extension Center and the Pine Tree Research Station, respectively. Redox sensors collected redox potential data in the soil and a data sonde was used to measure floodwater chemical properties. Based on initial soil tests, the DeWitt silt loam was more nutrient rich than the Calloway silt loam. The mean floodwater temperature without rice was slightly greater than with rice present. Soil redox potential decreased differently in the two soils when no rice was present, and the DeWitt silt loam reached critical redox potentials at a later date after flooding. Redox potentials in the two soils with rice present decreased similarly and critical redox values for NO3- and CO2 reduction were reached between 20 and 25 and 45 and 50 days after flooding, respectively. It is apparent that paddy soils in Arkansas approach critical redox potentials needed for NO3- and CO2 reduction. Research is currently underway to measure N20 and CH4 emissionf from flooded rice soils in Arkansas.