Flood Level and Single Drawdown Effects on Rice Yield and Water Quality.

Management of rice flood level, including complete drawdown, affects rice yield and water quality. With decreasing water availability for agriculture and increased pumping costs, there is a need to reduce water use in rice production systems while maintaining or improving rice yields. Alternative water management practices, in particular midseason short-term drainage - a common practice for controlling water weevil – need further investigation to evaluate their effects on rice yields and water quality. One of the primary effects of water level drawdown in flooded fields is the effect on soil redox potential. Drainage and re-flooding of flooded rice soils has been shown to release nutrients, particularly nitrogen and phosphorus that could potentially stimulate growth. Allowing sufficient time for organic biomass (algae and soil residues) to decompose and mineralize may provide nutrients for readily available uptake by rice roots. In addition, by monitoring water quality of inflows and outflows of rice fields under various water management practices, we should be able to provide farmers with information on how to best manage their flooded fields from a water quality standpoint. This study will test the hypotheses that lowering the water table and introducing a mid-season drawdown will reduce pumping costs, stimulate rice nutrient uptake, increase rice grain yield, and improve water quality.