Calibration of the Jensen' Yield Prediction Model for Rice Crop Cultivated in the Northern Region of Vietnam

Water stress and sensitive coefficient of crops are important parameters, indicating the effect of water regime on productivity. They provide a scientific basis for management agencies and farmers to manage and operate their irrigation systems. A field experiment was carried out on an area of 450m(2), divided into 42 experimental plots with different cultivation methods (conventional and SRI) and under different water regimes. Measurement parameters of each plot included irrigation water, rainfall, in-flow, evapotranspiration, capillary water going up while the surface soil layer was revealing and drying, in/out underground water flows in cultivating soil layer, infiltration water, difference of water levels on the experimental plots at the beginning and end of the study. Evapotranspiration in each growth stages of rice crops and in each experimental plot was determined. Then Jensen's yield prediction model was calibrated to predict rice yield as affected by the water stress. The result revealed that if water shortage had occurred, the yield of spring rice which was cultivated following SRI methods would be less than that cultivated by conventional method. Moreover, the effects of water shortage in 1st and 2nd growth stages of conventional cultivated summer rice were less than that cultivated following SRI method in the same stages. The yield of rice crops cultivated following the SRI method was less affected by the lack of water in 3rd and 4th growth stages, as compared to that cultivated by conventional method.