A model to predict safe stages of development for rice field draining and field tests of the model predictions in the Arkansas grand prairie
Due to the cost of extracting water, effective and efficient utilization of irrigation water for rice (Oryza sativa L.) is critical to rice farm profitability. The objective of this study is to predict safe stages of development for draining rice. This objective has the potential of saving rice farmers water. A computer program has been developed to predict the stage of development for draining water from rice field soils at which the risk of reduced grain yield or milling quality from insufficient water is considered to be near zero. The parameters of the model are predictions of (i) temperature during rice reproductive growth stages (RRGS) starting at R3, (ii) timing of various RRGS, (iii) maximum amount of water used by the rice crop at each growth stage, and (iv) the water held in the soil profile after draining which is available to the rice crop. The central goals of the model are to allow draining at an RRGS in which (a) the danger of reducing yield and quality from water deficits is at a minimum and (b) water is conserved and land conditions for harvest are improved. Experiments to test the predictions were conducted in 2005 and 2006 at two Arkansas locations: Gillett and Stuttgart. An experiment was also conducted at DeWitt, AR, in 2006. Draining at stages of development predicted by the model did not affect yield milling quality relative to the control for any year or location. Predicted water savings from reduced irrigation ranged between $10.26 to $55.44 ha–1 depending on pump depth. Implementation of the program can save money, reduce tillage costs, and reduce unnecessary depletion of the aquifers.