Characters Of Nitrogen Nutrition In Ground Cover Rice Production System

With the increasing risk of water scarcity and demand of irrigation in agricultural production, water-saving production system has attracted great attention. Ground Cover Rice Production System (GCRPS) is one of the new developed water-saving systems. However, most of the study focuses on its effects on water-saving, yield and nitrogen use efficiency, while seldom on the dynamic of crop growth, yield formation and nitrogen absorption through the entire growing period.A two-year field experiment was conducted at the Huangtu village of Shiyan in Hubei Province in 2003 and 2004. The aims of the experiment are: a) clarify the rice growth and nitrogen use efficiency as affected by different cultivation systems, b) study the rice growth and nitrogen use efficiency under the ground cover rice production system (GCRPS) as affected by nitrification inhibitor or controlled-release fertilizers, c) study the rice growth and nitrogen use efficiency under the conditions of applying different amount of controlled-release fertilizer in GCRPS. Eight treatments with three replicates were compared: 1) paddy rice without N fertilizer; 2) GCRPS without N fertilizer; 3) paddy rice with urea; 4) GCRPS with urea; 5) GCRPS with N fertilizer and nitrification inhibitor; 6) GCRPS with CRF-A; 7) GCRPS with CRF-B; 8) GCRPS with CRF-A (105kg N.hm-2). The amount of N application was 150kg N.hm-2 in other applying-N-fertilizer treatments except No. 8 treatment. Main results are as follows:Without the application of N fertilizer, the yield of GCRPS plants is higher than that of paddy rice, which indicates the growth of rice under GCRPS is superior to that of paddy rice. With urea application, the growth of vegetative phase of rice in GCRPS is more prosperous than that of paddy rice, which leads to premature senility. Morover, yield of GCRPS is lower than that of paddy with the urea application. The dominant yield-determine factor is the number of grains per panicle, which is clearly reduced by the decrease of the percentage of filled spiklets in GCRPS. However, the yield in the GCRPS could be increased by the application of nitrification inhibitor or controlled-release fertilizer through improving crop growth during the reproductive phase of rice.The amount of N accumulation is not significantly affected either under GCRPS or paddy system, but the ratio of N accumulation at vegetative phase to reproductive phase is significantly affected by different cultivation. The application of nitrification inhibitor or controlled-release fertilizer could not affect the amount of N accumulation at vegetative phase, but significantly improve N accumulation at reproductive phase. Nitrogen use efficiency was reduced compared to paddy rice when applying urea in GCRPS, while it is improved by applying nitrification inhibitor or controlled-release fertilizer.The controlled-release fertilizer shows better effects on improving plant growth and N uptake than nitrification inhibitor. Moreover, the controlled-release fertilizer, which could continue to release nitrogen fertilizer during reproductive phase, is superior to that faster released CRF.Plant growth and N demand are better satisfied by the application of CRF during the entire growing period. The dose of N application could be reduced to 70% of normal dose to obtain comparable grain yield, when apply CRF to GCRPS.