Studies On Physiology And Ecology For High Yield Of Super Hybrid Medium Indica Rice And Its Control

In order to study the theory and techniques of increasing yield of super hybrid rice from point ecology and view of cultivation, super hybrid rice combinations, Liangyoupeijiu, Liangyou 0293, GD-1S/Rb207, and others, were used as materials to conduct experiments on ecological adaptability, cultivation mode and nitrogen application rate in Sanya, Hainan province and Changsha, Hunan province in 2004-2007. The main results are as follows:(1) A series of high-yielding super hybrid rice combinations, such as Yyou173,88S/jin18,YHH-5,88S/R24-6,GuangXiang24S/R28-3-2,8Liang you45, C815S/45, G8S/R28-3-2 and others, were screened out. Their common characteristics are having more effective panicles, higher seed setting rate, medium and higher 1000-grain weight. The ideal modes are planting by wide-narrow-row and ridge cultivation. Ridge cultivation heightened yield mainly by promoting tillering and narrowing flag leaf angle. The appropriate planting density of those combinations which have strong tillering capability is 120000 hill/ha, and those with weaker tillering capability is 150000 hill/ha.(2) To attain the yield target of about 12 t/ha, the appropriate nitrogen application rates were 225 kg/ha and 300 kg/ha in Changsha region and Hainan region respectively, and the ratio of basal-fertilizer to dressing-fertilizer is 5:5-6:4.(3) The characteristics of functional leaves were affected by nitrogen application rate. When nitrogen application rate was increased, the length and width of flag leaf were increased, and the leaf angle of flag leaf showed trend of increase-decrease-increase. SPAD of leaves were increased with the increment of nitrogen rate and the decrease of density. Photosynthesis rates of leaves were significantly increased by nitrogen application rate.(4) Nitrogen application at an appropriate level could promote the growth, downwards movement and activity of rice roots, while excessive nitrogen fertilizer had restraining effect. Nitrogen application rate evidently affected the layer distribution of roots and the excreting amount of IAA and ABA of roots at panicle-differentiation stage, and the amount of different nitrogen rate treatments showed the trend of N₂>N₁>N₃> N₄. The distribution and excreting amount of IAA and ABA of roots were not affected by planting density.(5) Under condition of the same total fertilizer application rate, the increase of the proportion of panicle-fertilizer could prevent the premature senility of roots and leaves, at the same time, application of K fertilizer at booting stage could enhance these effects. Panicle fertilizer by panicle fertilizer + grain fertilizer + foliage dressing instead of application of panicle fertilizer only could significanly prolong the life of functional leaves, which was advantageous to heighten yield of super hybrid rice.(6) Density and fertilization had clear interaction on super rice. Yield and effective panicle number of N₃M₃ (medium fertilizer-high density) were highest. 1000-grain weight was not affected by density, But it was significantly decreased by increment of nitrogen rate. Effect of nitrogen rate on yield formation of super hybrid rice mainly, was in panicle number under lower nitrogen rate and in grain number per panicle under higher nitrogen rate.(7) Number of rhizosphere microorganisms was significant different in different nitrogen treatments, and it was affected by density at the same time. The change of number of rhizosphere microorganisms during whole growth duration was different in different nitrogen treatments. Change of activity of different rhizosphere microorganisms after a cropping showed disaccord, and the decreasing extent of microorganism activity was related to nitrogen rate and density. Activity of microorganism was decreased by the increment of application rate of N, P and K. Number of PAM bacteria at tillering stage was evidently increased by application of bacterium fertilizer, and number of K-bacterium was increased along with the growth stages but it was not affected by K fertilizer.