Impact Of Fertilizer-N Application In Different Seasons On The Rice Yield Growth Physiology And Variation Of Nitrogen Status In Soils

The Average rate of N application for rice production in China is higher but fertilizer-N use efficiency (NUE) is lower than the major rice growth countries. The measure with applying fertilizer in enriching the soil, improving the productivity of paddy fields, leads' to the high indigenous N content of soils and lower N use efficiency of fertilizer N application. This research was carried out in Hunan Agricultural University from 2002 to 2003. The objectives are: (1) to reveal the difference of nitrogen-providing capacity of paddy through the long-term localization experiment fertilizer-N application in different cropping seasons.(2) To determine the effect of fertilizer N application on growth physiology, yield and variation of nitrogen. The results showed as following:1.The effect on yield and yield componentsAfter two successful years'research, nitrogenous fertilizer was applied in the early rice, the yield increases 684.9 kg/hm2 when nitrogen was applied to the late rice continually, otherwise 1284.0 kg/hm without applying in late rice. Compared with the yield result, the yield without N application in early rice is not lower than with N application. The yield increased 1025.1 kg/hm2 and 1513.5 kg/hm2 respectively. Whether application of N or not has no obvious effect on the yield construction of late rice. The increase production is apparent with no application of N in early rice.2. The effect on dry production of early rice and late rice.In the condition of nitrogenous fertilizer was applied in the early rice, the dry production above the ground in mature stage increased 172.08 g/m2 if supplement in late rice and 320.18 g/m2 if not. In contrast, the dry production increased 129.40 g/m and 366.04 g/m2 respectively in the condition of no nitrogen application in early rice. The nitrogen amount applied in the growth stage has an important effect on dry production. Whether applying nitrogenous fertilize in early rice or not has no obvious impact on accumulation and distribution of dry production in late rice.3.The effect on nitrogenous status and fertilizer-N use efficiency.As to the nitrogenous accumulation of above-ground in the two years, T2 is the highest, and T3 is the lowest. Nitrogen fertilizers in early rice promote nitrogenous absorption in late rice. The nitrogenous Physiological efficiency in plot without N application is lower, which is extremely significant. 4. The correlation between various fertilize-N stages and change of N content in soil.During the growth stage of late rice in 2003, the change of whole nitrogen content in soil is slight. The utilization-N content of T2 is the highest, and T3 is the lowest. Rice absorbs more amino nitrogen. The content of amino nitrogen in soil is lower after harvest than planting, but the difference of content is not obvious.