Population Development Characteristics And Cultivation Strategies Of Late-sowing And Late-planting Rice Transplanted By Machine In Southern Jiangsu Province

As an efficient,productive and stable cultivation strategy,rice seedling transplanted by mechanization has turned into one of the major cultivation modes.In the course of agricultural practice,a lot of rice fields cannot be cropped in time for various reasons,generating the late-sowing and late-planting rice fields which are apparently delayed in transplant time.Late-sowing and late-planting rice transplanted by machine is prevalent,especially in rice-wheat cropping areas of southern Jiangsu province,becoming significant factors which restrict the realization of high and stable rice yield.There are many researches on the rice cultivation while the related studies on late-sowing and late-planting rice transplanted by machine remain lagging.This study observed the yield formation,population development characteristics and dry matter accumulation of late-sowing and late-planting rice transplanted by machine,explained the effects of cultivation measures on population development and yield formation and explored the factors limiting the yield of late-sowing and late-planting rice transplanted by machine and the cultivation strategies to improve the rice quality.The results can provide necessary theoretical foundation and practice support for establishment of efficiently technical systems.The main results were as follows:1.Compared with mechanical transplanting rice with normal sowing time,the yield of late-sowing and late-planting rice transplanted by machine decreased to some extent,number of panicles and number of grain per panicle being the main effect factors.The dry matter accumulation,output rate of dry matter in stem and sheath,conversion rate of dry matter in stem and sheath,economic index,non-structural carbohydrate(NSC)and apparent translocation amount of NSC were all in decline in heading stage,20 days post heading and maturation stage,while the crop growth rate showed a sign of increasing.2.In condition of late-sowing and late-planting,the yield of mechanical transplanting rice increased as the density increased,while the yield fitted the tendency of first rise then descend with the increase of nitrogen use of panicle fertilizer,and the peak yield appeared in the condition of medium panicle fertilizer.The same tendency was found in the accumulation of dry matter from aerial part.Output rate of dry matter in stem and sheath and conversion rate of dry matter in stem and sheath tend to first rise then descend with more nitrogen use through panicle fertilization.The concentration of NSC showed no obvious differences between density treatments,but it declined with the increase of panicle fertilizer application.On the whole,the crop growth rate increased with the increase in density while it tend to fist rise then descend with the increase in nitrogen level,from heading stage to maturation stage.3.In the earlier stage of late-sowing and late-planting rice transplanted by machine,the percentage of productive tillers decreased with tillers growing faster,the growth cycle decreasing and the tiller peak shifting forward.To some degree,the late-sowing and late-planting rice reduced the total leaf number of stem.Also,the leaf area index and the effective leaf area ratio ascended.Density and the application of medium panicle fertilization had the effect of improvement.According to the correlation analysis,the leaf area index of heading stage and maturation stage share strong relevance.4.The delay of sowing time lead to the degradation of rice appearance quality,but the cooking and eating quality increased slightly.The content of protein and every protein group seemed to first rise then descend.But the characteristics of RVA worsened,with peak viscosity,hot paste viscosity,breakdown and cool paste viscosity were all in decline,while setback,peak time and pasting temperature were all in rise.With more application of panicle fertilizer,the processing quality and appearance quality tend to first rise then descend,while the content of amyloses and proteins increased,among which albumin was most sensitive to the nitrogen use of panicle fertilizer.5.In mature stage,the nitrogen uptake in unit area presented the tendency of declining,as well as the nitrogen utilization.With the increase in panicle fertilization,the nitrogen uptake increased in the same way,while the recovery efficiency of nitrogen tend to first rise then descend and the physiological efficiency showed the sign of falling.6.The contents of lignin and cellulose decreased in late-sowing and late-planting rice transplanted by machine,yet the lodging index ascended to some degree.The increase of density and nitrogen panicle fertilization led to the decline of lignin and cellulose in stem sheath.