Nitrogen Optimization Simulation Studies Based On Effect Of Rice Growth And Nitrogen Environment

The effects of nitrogen fertilizer on the dynamic development of weight and nitrogen of rice organs, yield, N accumulation dynamic in the soil and rice-soil-leakage water system under different N application levels in paddy rice field were conducted inYuhang in 2003 and in Fuhang, 2004. Based on former experiments and our results, a established Rice fertilizer-N Optimization Simulation Model(RNOSM) was used to optimize the nitrogen application amount and time. Furthermore, a web-based simulation module for calculating parameter of RNOSM in Internet was also developed.The experimental and simulated results are shown as follows:1. There was significant correlation between applied nitrogen amount with LAI, dry weights of rice organs. Dry weight of green leaf, panicle and LAI increased quickly with the N application up to 225 kghm^-2, but declined when N supply exceeded 225 kghm^-2 .2. There was significant correlation between nitrogen applied levels with N content in leaf, stem, root, panicle and the coefficient are 0.9273, 0.9374, 0.8278, 0.9220 respectively.3. The yield was increased with N application added among proper range. Extra N application will reduce rice yield. The result inYuhang showed that yield reduced when N application amount exceeded 225 kghm^-24. Nitrogen accumulation dynamic in soil showed that the long-term fertility for rice crop growth could not be sustained when 75 kghm^-2 N applied each year, but when N supply exceeded 225 kghm^-2, surplus nitrogen was accumulated in soil. N accumulation in soil increased quickly and the peak of N content in leakage water appeared after basal nitrogen applied, which implied that basal nitrogen fertilizer being more than 50% of the total applied amount may be the main reason leading to soil nitrogen accumulation and water pollution.5. We suggested 225kghm^-2may be better N application inYuhang considering the N use efficiency6. The optimal economic yield of rice indicated that 199 kghm^-2 , 173kghm^-2 was the reasonable N application to rice variety Bing 9363, Bing 9652 in Yuhang, while 235 kghm^-2 was better N application to Bing 9363 in Fuyang.7. RNOSM simulation showed there was significant correlation between the observed and simulated biomass biomass, N in leaf, N in plant, they accord to "y=x".8. The result of RNOSM optimization showed that at low N application level (75kghm^-2),nitrogen fertilizer should be applied within 40 days after transplanting; at moderate N application level(150 kghm^-2),it should be applied within 55 days after transplanting ;at high N application (>150 kghm^-2),it should be applied within 70 days.9. Based on optimization of 150kghm^-2 in Yuhang , 225kghm^-2in Fuyang ,wesuggested N application should be applied at 10,20,30,45 days after transplanting with the fraction of 20:30:30:20 respectively.10. We developed web-based simulation module for calculating parameter ofRNOSM in Internet, it offered calculating online.