Development of Realtime Prediction System of Developmental Stage of Rice

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A model was developed for simulating rice crop developmental process, such as the onsets of ear initiation, spikelet formation, meiosis, heading and of maturation, in relation to daily temperature and day length conditions. In this model the crop developmental stage was quantified by a continuous value termed developmental index, DVI, of which value was defined to be zero at emergence, 1.0 at Panicle initiation, 2.0 at heading and 3.0 at maturation. Under this defining condition, DVI at any moment in time can be given by integrating developmental rate, DVR. We have proposed an equation to give DVR as a function of daily mean temperature and day length, and developed a computer program to estimate the parameters of DVR equation from data set on the crop phenology and the environments under field conditions.Twelve major rice cultivars were grown at 5 different Places which covered almost entire climatic regions in Japan for two years, and measurements were made of the crop phenology and environments. By use of the data thus obtained, the parameters of the DVR equation were determined for the 12 cultivars. The model together with these parameters explained the developmental stages of each cultivar from time course of the environments, within an error of 2 to 3 days.A realtime prediction system for developmental stage of rice was developed by connecting weather sensors to the computer system in which are built the model for predicting the phenological stage from the course of the environments and data base on past weather conditions for seven locations. A field trial with this system showed that the system predicts rice phenological stage very satisfactory to provide necessary information for the crop managements.