Effects Of Nitrogen Strategies On Population Quality And Grain Yield&Quality Of Strip-relay-intercropping Wheat

Using Chuanmai42, the major wheat cultivar in local production, a two-year field experiment was carried out in Sichuan Province from November2009to May2011under two-factor split-plot design. The main-plot was for N application rate in four levels (90,135,180,225kg/ha), and the sub-plot was for N application pattern with the ratio of base fertilizer, seedling fertilizer, jointing fertilizer, booting fertilizer in four levels (10:0:0:0,7:3:0:0,7:0:3:0,5:1:2:2). The effects of nitrogen managements on tiller development, dry matter production, carbon and nitrogen assimilation, the grain yield&quality was studied of strip-relay-intercropping wheat in Sichuan hilly areas. The main results showed as follows:1. The yield was increased at first and then decreased, and reached its largest value at the nitrogen rate of180kg/ha in two years experiment. In aspect of yield components, spike number had the same performance as yield, while seeds per panicle was significant increased with increase of nitrogen levels, and there were significant differences between treatments, but the differences of1000-grain weight was not significant. Simultaneously, spike number, seeds per panicle and the ear-bearing tiller percentage were all improved effectively at the dressing ratio of7:3(base fertilizer: jointing fertilizer). In general, the spike number, number of seeds per panicle and1000-grain weight were optimal under the nitrogen amount of180kg/ha combined with dressing ratio of7:3(base fertilizer:jointing fertilizer), and the highest grain yield was4800.4kg/ha(4706.4kg/ha in2011).2. Leaf area index (LAI) of wheat after jointing, and the dry matter accumulation were increased with increase of nitrogen levels, while grain-leaf ratio was increased at first and then decreased, and the ratio reached its largest value at the nitrogen rate of180kg/ha. Simultaneously, the LAI after flowering, the dry matter accumulation per day and grain-leaf ratio were all improved effectively at the dressing ratio of7:3(base fertilizer:jointing fertilizer). The results of correlation analysis showed that the LAI after booting, the dry matter accumulation at booting and the dry matter accumulation per day were significantly correlated with grain yield.3. The application of nitrogen fertilizer increased the flag leaf chlorophyll content effectively, promoted the accumulation of NSC after flowering and improved its contribution rate to grain NSC, but excessive nitrogen fertilization was adverse to the transfer of soluble sugar (WSC) in stems and sheaths to grains, and the NSC accumulation and its contribution rate to grain NSC were reduced after flowering, too. so it was not conducive to the accumulation of NSC in the grain; nitrogen fertilizer used at different stages could significantly improve the flag leaf chlorophyll content, promote the accumulation of NSC after flowering and increase the efficiency to grain NSC contribution rate, especially used in the jointing stages. Carbon and nitrogen metabolism was optimal under the nitrogen amount between135and180kg/ha combined with dressing ratio of7:3(base fertilizer:jointing fertilizer), and the C/N value of leaf at anthesis was between2.72to3.044. The total N accumulation of aboveground plants in maturity increased significantly with the application of nitrogen fertilizer. The nitrogen accumulation in vegetative organs at flowering as well as in the leaf and stem at maturity were increased with the increase of nitrogen levels, and the contribution rate of translocated N to grain exhibited the same tendency, but the nitrogen assimilation post-anthesis and the contribution rate to grain ascended firstly and then declined with the increase of nitrogen levels, besides, the largest values appeared at the nitrogen rate of135kg/ha. Simultaneously, the nitrogen assimilation post-anthesis and the contribution rate to grain were improved effectively by the dressing ratio of7:3(base fertilizer:jointing fertilizer). On the other hand, the nitrogen application which dressing ratio was5:1:2:2(base fertilizer:seedling fertilizer:jointing fertilizer:earing fertilizer) promoted the translocation of storage nitrogen before anthesis from vegetative organ to grain effectively, and the residues nitrogen in vegetative organs at maturity increased, while the allocation proportion of nitrogen in grain decreased.5. N use efficiency and N harvest index and N productivity all decreased with the increase of nitrogen levels, but the total content of N and NO3-N and NH4-N in soil increased, and the performance was consistent between two years. N harvest index had its high value at the dressing ratio of7:3(base fertilizer:jointing fertilizer), the largest value was71.9%.6. The content of protein and wet gluten in grain increased as the amount of nitrogen increased, the sedimentation value had a decrease after an increase as the amount of nitrogen was increasing, it peaked at135kg N/ha, there were no significant differences of protein content between different treatments, but the differences of wet gluten and sedimentation were significant. The application of base fertilizer:jointing fertilizer=7:3was beneficial for the improvement of protein content, wet gluten and sedimentation value. In conclusion, when the nitrogen amount was135～180kg N/ha with dressing ratio of7:3(base fertilizer:jointing fertilizer), there were appropriate population at early growth stage, more effective tillers and higher ear-bearing tiller percentage. Simultaneously, the LAI and dry matter accumulation rate were kept high level after anthesis, carbon and nitrogen assimilation ability was strong, the degree of carbon and nitrogen metabolism was high, and matter translocation after anthesis was promoted effectively, so that number of seeds per panicle and grain capacity were increased, and the higher yield was obtained. The protein content of grain and the quality of wet gluten was high simultaneously. As far as nitrogen utilization was concerned, it could improve nitrogen use efficiency and harvest index of nitrogen, and reduce the residual nitrogen in soil, so that the danger of pollution lead by residual nitrogen was reduced. It was the appropriate nitrogen application pattern to get high yield and quality, ecological safe wheat in hilly and dry land in Sichuan planted under relay-strip-cropping-system. The result showed that the appropriate population indexes for strip-relay-intercropping wheat in Sichuan hilly areas were184.5×104/ha of the seedling number,225.3×104/ha of the spike number,72.8%of the spike rate,4.68of the highest LAI at booting,2.11of LAI at filling,1600.6kg/ha of post-anthesis dry matter accumulation,9652.5×104/ha of seeds number and11.501mg/cm2of grain-leaf ratio, respectively.