| The experiment was conducted to examine the amounts of nitrogen and dry matter accumulation as well as their translocation dynamics and physiobiochemical mechanism in ratoon rice exposed to different nitrogen application rates to further understand the properties of N absorption and its effect on yield. The results were summarized as follows:1. Nitrogen accumulation and its translocationThe parabola curve could be used to describe the relationship of N absorption and its recovery rate with nitrogen application rates to promote bud and tiller in main rice and its ratoon crop. After nitrogen fertilizer was applied to promote bud and tiller, the amount of N absorption decreased with the growing time courses increasing. About 1/3 amounts of N absorption from the nitrogen fertilizer applied to promote bud and tiller was deposited in the main rice stubble. The total amount of N accumulated in the stubble absorbed from applied nitrogen fertilizer and original nitrogen element in paddy soil was closely related to nitrogen application rate for bud and tiller, exhibiting a parabola curve. And the nitrogen source in the stubble of main rice was gradually transported to the tillers of ratoon crop after main rice was harvested, performing the largest transported amount with 29%-54% in surface transportation rate, which was believed to play a great role in bud sprouting and tiller growing. N accumulation in the leaves and stem-sheath of ratoon rice increased as nitrogen application rate was enhanced, a large amounts of N in the parts of ratoon rice were transported to the panicles after full heading. The surface transportation rate was 57%-76% in consideration of N translocation from the stubble of main rice. This indicated that the nitrogen transported from the stubble and the other parts; including leaves and stem-sheath was the main nitrogen source deposited in grains of ratoon rice.2. The effect of nitrogen fertilizer on the yield of ratoon riceThe photo-production was significantly enhanced in main rice exposed tooptimum nitrogen application rate used to promote bud and tiller, in turn resulted inincreased dry matter accumulation in leaves and stem-sheath, thereby the stubble ofmain rice had the larger share in the dry matter weight after harvesting, then the drymatter accumulated in the stubble could be good enough to transporte to the tillers of ratoon crop. The result also indicated that the optimum nitrogen application rate used to promote bud and tiller significantly increased the photo-production of ratoon rice, attributed to increasing the number of productive tillers and the leaf areas, consequently increased leaf areas of population and its growth rate. It was also found that the optimum nitrogen application rate had very important role in increasing transported rate of dry matter from the stubble and leaves of main rice, leading to significantly increase the accumulation of dry matter in ratoon rice crop. The net accumulation of dry matter in the period from full heading to ripening in ratoon crop, panicle number of ratoon crop and grain yield were parabolically related to the nitrogen application rate used to promote bud and tiller. The grain yield of ratoon crop exposed to 24.14 g.Nm"2 was the highest.3.The effect of nitrogen fertilizer on yield and its physiobiochemical mechanismThe result from this experiment showed that the activity of nitrate reductase(NR) in the leaves of ratoon rice was increased as nitrogen application rate was enhanced. The same trade was also true in the cases of chlorophyll contents, net photosynthetic rate, leaf areas and photosynthesis of population ( crop growth rate and net photo-production ). This in turn resulted in increased dry matter accumulation which was considered the physiological basis to produce high grain yield. The biochemical analysis indicated that the optimum nitrogen application rate alse increased the activities of cell defense enzymes, thereby reduced manbrane detriment by active oxygen species produced in environmental...
|
PDF Full Text Request