Effects Of Nitrogen Application Of Yield Formation Of Late Rice And Its Mechanism Under Full Amount Straw-returning

In order to investigate the effects of nitrogen application under the full amount straw returning on grain yield and quality of late rice, used the late season rice GanXin 688 as materials, the experiments were carried out during 2009 and 2010. The main results were as follows:1,Effects of straw returning on grain yield and its components:Compared with control(no straw returning), the full amount of straw returning increased effective panicles, filled grain rate and 1000-grain weight, but reduced grain number per panicle and promoted rice yield. Straw returning enhanced the percentage of productive tiller and the biomass and the utilization of nitrogen,and delayed the leaf senescence after heading.The rice appearance, cooking and eating quality are improved.2,Effects of the nitrogen application on grain yield and its components as well as the rice quality after straw returning:(1)A parabola relationship was found between the nitrogen application rate and the grain yield and with nitrogen 180 kg/hm2, the yield was highest. With same nitrogen application rate(180kg/hm2), the yield is highest under the ratio of basal nitrogen:tiller nitrogen:panicle nitrogen was 5:2:3.With the nitrogen application rate increased, the percentage of productive tiller was declined. The number of primary branch differentiation and large vascular bundles in the uppermost internode are both most nuder nitrogen 180 kg/hm2. The ratio of grain number to large vascular bundle is lowest when basal nitrogen:tiller nitrogen:panicle nitrogen was 5:2:3.(2) The more nitrogen application, the higher biomass and LAI.The translocation of dry matter in stem and sheath and its contribution rate to yield were highest under the nitrogen application level was 180kg/hm2. With same nitrogen application rate, the more nitrogen application level, the higher biomass. The translocation of dry matter in stem and sheath and its contribution rate to yield were highest under basal nitrogen:tiller nitrogen:panicle nitrogen was 5:2:3.(3) When nitrogen application increasing, the total N accumulation,the N using efficiency and the needed nitrogen for produced 100 kg of grain.The N agronomic efficiency was highest under the nitrogen application level was 180kg/hm2. With same nitrogen application rate, the N agronomic efficiency and N physiological efficiency were highest under basal nitrogen:tiller nitrogen:panicle nitrogen was 5:2:3.(4) The more nitrogen application, the higher the plant height and the top three leaves.The flag leaf and bend angle of pour trilobites were largest under the nitrogen application level is 180kg/hm2. An higher spikelets-bleeding-intensity temperature depression(difference between air temperature and flag leaf temperature), flag leaf SPAD and net photosynthetic rate, and smaller the degradation rate of root acticity after heading were found as nitrogen application increased. With same nitrogen application rate, the degradation rate of root acticity were lowest under basal nitrogen:tiller nitrogen: panicle nitrogen was 5:2:3. Net photosynthetic rate of the flag leaf in full-heading stage was highest under the nitrogen application level was 180kg/hm2 and basal nitrogen: tiller nitrogen:panicle nitrogen was5:2:3.(5) When nitrogen application level increasing, the soil temperature reduced. With same nitrogen application rate, the soil temperature in 5cm and 10cm were highest under basal nitrogen:tiller nitrogen:panicle nitrogen was 5:2:3.(6) As nitrogen application increased, the rate of husked was rised and the percentage of grains with Chalkiness was lower. With same nitrogen application rate, the more panicle nitrogen, the higher the rate of husked and milled rice.