Research And Demonstration Of Integrated Rice (Oryza Sativa L.) Management Technology For High Yield And High Nutrient Use Efficiency In Cold Region

To feed the increasing population and improve the resources use efficiency (RUE), the goal of rice (Oryza sativa L.) production is to achieve high grain yield and high RUE simultaneously. This study has focused on the rice production in cold region in Heilongjiang Province, with Qixing Farm as a case study, to identify the limited factors to improve yield and then develop an integrated rice management system (IRM). Initially, through intensive farm surveys, the potential and constrains for further increasing grain yield and RUE were investigated. Using results of ten field experiments, this study analyzed the influence of rice development and yield components on final yield, and the dynamics of dry matter and nitrogen (N) accumulation. Based on the above analyses, together with the reported results for current optimized rice management in literatures, we have developed the IRM, which included the optimization of density, nutrient and water management. Meanwhile, IRM was validated by field trials to evaluate the agronomic performance on population quality, yield and RUE. Finally, the IRM was further applied to different sizes of farms to further explore the effect, prospects and problems of IRM application over large areas. The main results were as follows:(1) Through farm surveys, simulations with Oryza2000model in our group, together with the recorded yield, we found local rice still has the potential to increase yield by30-54%and RUE by19%. The factors to constrain grain yield improvement included (a) Limited understanding of variety characteristics;(b) Lower planting density with more than60%of farmers below27hills m"2;(c) Improper timing of N application, with nearly90%of N fertilizer being applied at the early growth stage and half farmers not applying topdressing N fertilizers;(d) Unsuitable P and K fertilization, with50%of farmers overused phosphate fertilizer and40%of farmers failed to applied enough potassium fertilizer;(e) Improper water management, with many farmers still believing that rice need continuous flooding for whole growing season.(2) Through ten field experiments, we found yield improvement relied on panicle number per unit area and dry matter accumulation, and was less affected by grains per panicle and harvest index. Yield was not significantly affected by spikelet fertility and thousand grain weight. Panicle initiation to heading stage was the most important and fastest stage for dry matter and N accumulation. N and dry matter accumulation from panicle initiation to heading and post-anthesis had the most important influence on grain yield.(3) Based on the above analysis, together with the reported results for current optimized management in literatures, we have developed the IRM and verified it in fields. Compared with farmers’ practice, the N recovery use efficiency (RE), N agronomic use efficiency (AE), and N partial factor productivity (PFP) were improved by63%,46%, and49%, respectively, if only water and N management were optimized while grain yield was maintained. Compared with fanners’ practice, the IRM improved the RE, AE and PFP by97%,95%, and51%, respectively, while grain yield was increases by10%. Meanwhile, the IRM increased the population quality and reduced the risk of lodging in large extent. Compared with the high yield system,21%of N fertilizer was reduced in IRM while high grain yield was maintained. Meanwhile, AE and PFP were improved by22%and27%, respectively in IRM.(4) The IRM has been further applied to different sizes of farms as demonstrations. The results showed IRM could increase grain yield, PFP and AE by9%,10%and26%, respectively. However, the percent of improvements in yield and NUE was reduced from small demonstration fields, technology influenced fields to large extension fields. These differences were caused by simplification of management, technology contamination and technology limitations, etc.