Study On Technique Of Precise Determination Of Nitrogen Fertilizer To Improve Quality And Yield Of Rice

A series of experiments were conducted at different ecological regions in Jiansu Province, including Kunshan City(Yushan Towm) and Xishan(Yangjian Town) in Taihu area, Taixing City (Gensi Towm) in area along Yangtze Rive with high sand soil, Gaoyou City (Gaoyou Towm) and Jianhu County(Shanggang Towm) in Lixiahe area and Donghai County(Pingming Towm) in Huaibei area, during 2000-2001. For calculating the total amount of N application, three parameters of Stanford formulae, i.e. N requirement of the expectant yield, N fertilizer recovery and N supplied in the soil, were studied with the pairwise comparison experiments in applying vs no applying nitrogen under the grain yield 650-700Kg/667m2 of major Japonica varieties. On basis of above analyses, with the exception of calibrating three parameters, the validating experiments, about the feasibility of using Stanford formulae and the harmony between high yield and good quality, were carried out in the different basic fertility soil at Kunshan , Gaoyou and Donghai during 2001- 2002. The main results were as follows:(l)There was a parabola relationship between the yield of N-applying and the corresponding N-quantity of consumption to produce 100kg grains. The parabola equation was Y=-1384.7x2+5928.5x-5668.3 (R=0.7849**: n=91). The N-quantity of consumption to produce 100kg grains in the most Japonica varieties was relatively stable and 36 samples centralized on the range from 1.9kg to 2.3kg, average 2.1kg, under the yield 650 to 700Kg/667m2. So the 2.1kg can adapted to the most Japonicavarieties under the high yield.(2) There was a significant positive correlation between rice yield of N-applying with N recovery in this season under N-application at 15-23 kg/667m2 in different basic fertility soil. The 40% is the low-limit of critical index of N-recovery to obtain the expectant yield 700Kg/667m2.(3)There were significant positive correlation between rice yield of no applying N (indicate soil fertility), the content of alkaline hydrolytic N, total N and organic matter in tillage layer (0-20cm), rice yield of N-applying and N-supplied in the soil of no N-applying. They can be adopted as an index to diagnose and forecast N supplied in the soil. Contraposing the actual condition of being unaware of the rice yield of no applying N in this season, the content of alkaline hydrolytic N, total N and organic matter should be needed chemical analyses, the way was discussed to forecast N supplied in the soil according to yield of previous rice or other crops (the normal years and management).(4) The results of the validating experiment showed that Stanford formulae used to calculate the total amount of N application is feasible at Kunshan, Gaoyou and Donghai. The N-quantity of consumption to produce 100kg grains of the expectant yield(700Kg/667m2) 2.1kg and N fertilizer recovery 40% are credible. The accuracy of calculating the total amount of N application was primarily related to the fitness between the predication data and the actual data of N supplied in the soil.(5)On the base of applying excellent cultivars, high yield and good quality may be well coordinated at a relatively high level under applying total amount of nitrogen that can attain expectant yield. On the contrary, obvious contradictions existed between high yield and apparent qualities. Among them, chalkiness rate and chalkiness area were high that affected the grade of rice quality. In order to solve the contradictions, it should properly reduce amount of nitrogen and choose suitable rice variety with good quality.