Predictive analysis of late rice potential productivity in Dongting Lake Area (DLA) based on stepwise diminishing method
The Dongting Lake Area(DLA),a famous and important commodity grain production base in China,is one of nine industrial belts of the top agricultural products,and belongs to the top grain industrial belt of double-cropping paddy in the Yangtze River Basin.Therefore,the investigations based on the rice productivity of the DLA is vital for the optimization of the land resource allocation,assessment of the paddy field ecosystem,design of agricultural development plan and protection of agricultural eco-environment.According to the meteorological analysis data from 2003 to 2007 and the soil analysis data of the Second National Field Survey,utilizing the stepwise diminishing method of light,temperature,water and soil,a comparative research was carried out to build an appropriate rice potential productivity model for the DLA.Two rice potential productivity models(photosynthesis-temperature potential productivity calculation by step-by-step model and FAO-AEZ model) were investigated,followed by the analysis of the spatial distribution of late rice potential productivity with the assistance of Geographic Information System(GIS).The results showed that the mean simulation value of five years(2003-2007) predicted by a step-by-step model achieved 7808.072 kg/hm2,higher than the observation value(5904 kg/hm2);while the simulation value obtained by FAO-AEZ model was only 5687.45 kg/hm2,even lower than the mean observation value,which is unreasonable for the actuality of DLA.This disclosed that the model based on step-by-step calculation of photosynthesis-temperature potential productivity was appropriate to predict the late rice potential productivity in the study area.At the same time,the research also revealed that the late rice potential productivity in the DLA decreased gradually from northwest to southeast.The regions of Lixian,Anxiang,Hanshou and Linli counties in Changde city contributed high or medium yields,while the low yield areas were mainly distributed in Changsha,Yiyang and Yueyang cities.The late rice potential productivity of the DLA was inadequate,and the low yield area occupied 45% of the total DLA,which exhibited great potential for the improvement of the late rice yield by means of sound tillage control measures,including rational fertilization system and water management.