Simulating the optimal growing season of rice in the Yangtze River Valley and its adjacent area, China

With a focus on the dependence of rice production on climatic conditions, a model was presented to simulate the growth and development of different rice genotypes, Simulations of biomass growth responded to daily solar radiation and temperature for a given genotype. The contributions of photosynthate produced before and after heading to grain yield and the effect of temperature on grain filling were incorporated into the growth model. Simulation of plant phenological development was driven by daily temperature and day-length. Model predictions of biomass accumulation and grain yield formation were validated against field measurements and good agreement between simulated and observed data sets was obtained. By applying the developed model to the Yangtze River Valley and its adjacent area, which covers approximately 70% of the total rice cropping area in China, the optimal growing seasons under local climatic conditions and cropping systems were simulated and the relevant grain yields were predicted for four lice genotypes (hybrid indica, medium indica, medium japonica and late japonica). Simulations showed that the optimal sowing dates are between 10 April and 20 May and the corresponding heading dates occur in the period from the end of July to the end of August. The simulated grain yields under these optimal growing seasons vary from a value of 7.90-11.25 t/ha. Observations from various locations indicated that grain yields obtained within the optimal planting period were higher than those outside the optimal period. Calculations suggested that an average increase of 10% in grain yield is possible when rice plants are planted within the simulated optimal period, approximately 10 days earlier than current planting dates. (C) 1998 Elsevier Science B.V. All rights reserved.