Studies On The Population Characteristics And Nitrogen Uptake And Utilization Of Super-high Yield Of Double Cropping Early Rice In The Middle Reaches Of Yangtze River

The experiments were conducted in the Yangtze River in Jiangxi double cropping areas inYuanzhou and Poyang two places from 2007 to 2009, local main variety: xiannong31 and luliangyou28 were adopted as material. Through a large area follow-up survey,we studied the population characteristics and nitrogen uptake characteristics of three types of population:middle-yielding(yield≤500kg/666.7m2) , high-yielding (yield:500-600kg/666.7m2) and super-high-yielding (yield≥600kg/666.7m2) three types of population.The main results were as follows:1,Compare with high-yielding and middle-yielding population, The formation characteristics of super-high-yielding were as follows: (1) In the super-high yielding components, panicle number to yield show the greatest contribution, followed by grains, there was no significant difference between filled-grain percentage and 1000-grain weight; Therefore, based on the appropriate increase in the high spike at the same time capture a large ear, and make further efforts improving filled grain percentage and 1000-grain weight is the basic characteristics of super-high yielding early rice. (2) The expected number of panicle was achieved at the critical stage of productive tillering and the maximum number of stems and tillers was achieved before the stage of joining. The leaf area index (LAI) was reached maximum at the stage of heading and the ratio of spikes to tillers > 60%. (3) The final biomass yield of population was increased by strengthening dry matter accumulation during grain milking stage through the proper accumulation of dry matter during the medium period. Before the jointing stage, the dry matter accumulation of super-high-yeilding population nearly to the high and middle population. But at the jointing stage to heading and heading stage to maturity stage,the dry matter accumulation quantity significant or significantly higher yield and middle group。Economic yield and dry matter accumulation at maturity stage and heading to maturity stage showed very significant positive correlation.Similarity, the index of characteristics of super-high-yielding and using compared with the indexes mentioned above:(1) total spikelets>2.8×107·666.7m-2, filled-grain percentage>80%, 1000-grain weight is26-28g; (2) The expected number of panicle was achieved more than 80% at the critical stage of productive tillering and the maximum number of stems and tillers was achieved before the stage of joining and the ratio of spikes to tillers > 60%. (3) leaf area index at heading 6.3, photosynthetic potential during whole growth period>2.6×105m2·d/666.7m2, grain-leaf ratio (No of grain per cm2 leaf area)>0.54.(4) population material production capacity was achieved maximum at heading stage to maturing stage, population net increase quality of dry matter achieved 420kg.666.7m2, accounting for about 40%, total dry matter weight at maturity>1040kg·666.7m-2, formation availability>25%, from heading stage to maturity stage CGR>14 (g/m2·d),NAR>3 (g/m2·d).Compare with high-yielding and middle-yielding population,during the transplanting, the nitrogen content of super high-yielding population plant is the same as the high-yielding and middle-yielding population;during N-n+1, the nitrogen content of super high-yielding population plant is less than another, the nitrogen content of high-yielding is less than middle-yielding's.In the jointing stage,heading stage and maturity stage, the nitrogen content of super high-yielding population plant is more than the high-yielding and middle-yielding population.The sequence of total nitrogen absorption content is super high-yielding population> high-yielding population >middle-yielding population.Before N-n+1,the nitrogen content of super high-yielding population is higher than another, From jointing stage to heading stage and heading stage to maturity stage, the nitrogen absorption proportion super high-yielding population> high-yielding population>middle-yielding population.In the field of N absorption amount per 100kg grain,Nitrogen agronomic efficiency Nitrogen apparent productivityNitrogen utilization efficiency , super high-yielding population is higher than high-yielding and middle-yielding population.Similarity, the index of Nitrogen uptake and utilization compared with the indexes mentioned above:(1) nitrogen content(%):3.5in the transplanting,2.7 in the N-n+1,2.0 in the jointing stage,1.3 in the heading stage,1.0 in the mature stage, (2)plant absorbed nitrogen content (Kg/666.7m2):3.3 in the N-n+1, 6 in the jointing stage,9 in the heading stage,10.6 in the mature stage,Before N-n+1 plant absorbed nitrogen content accounted for 30%,from N-n+1 stage to heading stage, accounted for 45%～50%, from heading stage to maturity stage, accounted for 20%~25% .