Study On Optimal Design Of Rice Production Manage-Ments Based On Models

In China,more than 60%of the population uses rice as their staple food,and about 1/3 of the grain cultivated land grows rice.In the past 10 years,the yield per unit area of rice in China has been increasing slowly.With the continuous growth of population and the reduction of arable land area,it is urgent to improve the yield per unit area of rice.The crop growth model combines meteorological,soil and crop cultivation management measures,which can describ the relationships between crop growth status and the environment from a system perspective and quantitatively simulate the dynamic processes of crop growth and yield formation.Therefore,it can be used to provide optimal management decisions for crop production.This study is based on two typical sites（Nanjing for single rice and Nanchang for double rice）in China’s main rice producing regions,based on with field test data from 2007 to 2015 and the meteorological data from 1980 to 2015,three rice growth models,ORYZA（v3）,CERES-Rice and RiceGrow,were used to simulate and study the effects of different management measures on rice yield and nitrogen utilization efficiency by designing a single change of sowing date,transplanting density,amount of nitrogen fertilizer,times of nitrogen application and the ratio of base fertilizer and topdressing,as well as simultaneous change of sowing date and transplanting density,sowing date and amount of nitrogen fertilizer,transplanting density and amount of nitrogen fertilizer.The rice yield under conventional,high yield and high efficiency,super-high-yield mode and light temperature potential productivity mode with model characteristics were simulated,and the differences of yield and nitrogen utilization efficiency under different cultivation modes were compared and analyzed.This study will provide certain theoretical and technical support for optimizing rice field managements,increasing yield and resource utilization efficiency,and ensuring food security in China.The results indicate that the simulation results of the three rice growth models are generally consistent,but the simulated yield and absolute value of efficiency are somewhat different.The effects of different management measures on rice yield and nitrogen fertilizer use efficiency（NUE）also differ among different models and rice cultivation types.Comparing with the farmer’ prescription,under the change of single management measures,rice yield increases with the advance of the sowing date transplanting density and amount of nitrogen fertilizer,the increase of the frequency of fertilization or the proportion of top dressing under a certain amount of nitrogen fertilizer.The management measures have a significant effect on rice yield and their contributions to reducing the yield difference,and the order of performance on single rice are:the advance of sowing date（10.55%）,the increase of frequency of fertilization（10.30%）,and the increase of transplanting density（8.33%）,the increase of the amount of nitrogen fertilizer（0.66%）;for early rice:the advance of sowing date（16.98%）,the increase of transplanting density（10.05%）,the increase of the frequency of fertilization（6.15%）,the increase of the amount of nitrogen fertilizer（5.62%）,the increase of top dressing ratio（1.93%）;for late rice:the advance of sowing date（17.62%）,the increase of transplanting density（11.71%）,the increase of the frequency of fertilization（8.23%）,the change of the ratio of base fertilizer,tiller fertilizer,and spike fertilizer under the basis of（base fertilizer+tiller fertilizer）:spike fertilizer=8:2（0.50%）.Under the change of single management measure,the management measures that can improve the NUE for single rice are:the reduction of the amount of nitrogen fertilizer,the increase of fertilization frequency,the increase of transplanting density,the advance of sowing date;for early rice:the reduction of the amount of nitrogen fertilizer,the increase of transplant density,the increase of top dressing ratio,the advance of sowing date,and the increase of the frequency of fertilization;for late rice:the decrease of the amount of nitrogen fertilizer,the postponement of the sowing date,the increase of the fertilization frequency,and the increase of the transplanting density.Under the interaction of different management measures,the rice yield increases with the advance of the sowing date,the increase of the transplanting density,and the increase of amount of nitrogen fertilizer,and there is a complementary effect between the management measures.The combination of management interactions with increasing yield and their contribution rate for single rice are:the interaction between advanced sowing date and increased transplanting density（9.48%）,the interaction between increased amount of nitrogen fertilizer and increased transplanting density（8.52%）,the interaction between advanced sowing date and increased amount of nitrogen fertilizer（3.60%）,the interaction between reduced amount of nitrogen fertilizer and increased transplanting density（1.48%）;for early rice are:the interaction between advanced sowing date and increased transplanting density（13.63%）,the interaction between advanced sowing date and increased amount of nitrogen fertilizer（8.50%）,the interaction between increased amount of nitrogen fertilizer and increased transplanting density（8.38%）,the interaction between postposed sowing date and increased transplanting density（2.0%）,the interaction between decreased amount of nitrogen fertilizer and increased transplanting density（1.42%）;for late rice:the interaction between advanced of sowing date and increased transplanting density（9.89%）,the interaction between advanced sowing date and increased amount of nitrogen fertilizer（8.82%）,the interaction between increased amount of nitrogen fertilizer and increased transplanting density（6.33%）,the interaction between advance of sowing date and reduced transplanting density（0.23%）.Interactions of different management measures which have a general effect on improving the partial factor productivity of nitrogen are as followed:the interaction between advanced sowing date and increased transplanting density,the interaction between advanced sowing date and reduced amount of nitrogen fertilizer,the interaction between postposed sowing date and reduced amount of nitrogen fertilizer,the interaction between reduced amount of nitrogen fertilizer and reduced transplanting density,the interaction between reduced amount of nitrogen fertilizer and increased transplanting density.Through the comparative analysis of the yield and NUE of the conventional mode,high yield and high efficiency mode,super-high-yield and light temperature potential productivity mode,it is concluded that for single rice,early rice and late rice,the above-ground biomass and yield under the four cultivation modes are all conventional mode