CARICE - A RICE MODEL FOR SCHEDULING AND EVALUATING MANAGEMENT ACTIONS

Crop growth modeling can be useful in crop management, but previous rice crop models lack the morphologically accurate phenological detail needed for practical application. We designed a rice crop management model, CARICE, for scheduling management actions on the farm and evaluating consequences of alternative management strategies. A simple rice crop productivity model was expanded to include (i) phenology, based on leaf stage; (ii) tiller development, to establish yield components; (iii) assimilate partitioning by developmental stage, (iv) assimilate partitioning patterns of California cultivars; and (v) a direct-seeded cultural system. The key phenological events were accurately simulated: leaf stage development followed the expected pattern; predicted 50% heading was within 6 d of the actual heading dates; and grain filling predictions were within 1 to 11 d of field observations. Cultural management strategies simulated included delayed planting, and managing barnyardgrass (Echinochloa spp.; BYG) competition by increasing water depth and seeding rate. Simulated yield results were within the range of field observations, although total aboveground biomass was overestimated. The model simulated a 27% loss in grain yield from a 21-d delay in planting, which is close to the 21% loss measured in the field. At 11 and 54 BYG plants m-2, the model simulated 20.6 and 54.6% yield reductions relative to the control, as compared with 32.5 and 57.5% reported in the literature. The model predicted the interactive effect of rice seeding rate and water depth management for reducing barnyardgrass competition. The morphologically accurate phenology submodel and the yield-component approach to calculating yield are keys to using CARICE for scheduling and evaluating management actions and strategies.