Effect Of Nitrogen Management On Super-High-Yield Summer Maize And Its Physiological Bases

The production of super-high-yield summer maize is an important strategic way to improve the production of maize and ensure the national food security. At present phenomenons such as excessive fertilizer（especially nitrogen）、unbalanced nutrient ratio、unreasonable fertilizer application times and so on were widespread. Therefore it has the important theoretical and practical value to clear the limiting nutrient factors、yield responses to applied NPK and balanced nutrient ratio、the characters of assimilation and accumulation of nitrogen、appropriate nitrogen application and reasonable fertilizer application times and so on, then to realize the aim of high yield , high efficiency fertilization, simplify of super-high-yield summer maize. However, the reports about the nutrition requirement of crops and appropriate fertilization techniques of super-high-yield summer maize are rarely to seen. Therefore, in the area of high yield of summer maize of xunxian, Henan Province, according to different soils, we recommended balanced fertilization from 2007 to 2009. We also made research on the limiting nutrient factors and the characters of nutrient assimilation and accumulation of super-high-yield summer maize systematically; This paper focused on the characters of nitrogen assimilation and accumulation、economic optimum nitrogen fertilizer and its effect、the effect of postponing N application on increasing yield and its physiological bases、the effect of nitrogen fertilizer on yield and nitrogen absorption and utilization of different kinds of super-high-yield summer maize、the techniques of single application of base fertilizer （slow/controlled release N fertilizer） and its effect, which to provide theoretical basis and technological support for proper fertilizer management of super-high-yield summer maize.1. The research of soil nutrient restrictive factors and plant nutrient uptake and accumulation of super-high-yield summer maize showed that the maize yields are highest under the OPT treatment （By ASI）, 12051.2 kg·hm^-2 and 13246.3 kg·hm^-2 in 2007 and 2008 respectively. The nitrogen and potassium fertilization could evidently increase the yields by 8.92% and 7.14%, which indicates N and K are main nutrient restrictive factors. The accumulations of nitrogen, phosphorus and potassium of super-high-yield summer maize plants are increased with the extension of the bearing period, and the nutrient accumulation amounts are maximum at the maturity stage. The order of nutrient accumulations is K2O>N>P2O5, and the absorbed nutrient ratio with 100 kilogram maize of N, P2O5 and K2O are 2.40:1:2.73. The key period of nutrient absorption is from the jointing stage to silking stage, and the absorbed nutrient rates are the highest. After the silking stage, maize plant absorbs more nitrogen and phosphorus. Leaf is distribution center of nitrogen and phosphorus from the seeding stage to silking stage, and the transfer efficiency of nitrogen and phosphorus are higher in stems and leaves at the late stages, while the transfer proportion of potassium is small. Nutrients are absorbed continuously at the whole growth period of super-high-yield summer maize, it is essential to super-high-yield topdressing after the silking stage that ensure adequate nutrients at the grain filling stage. Balanced NPK fertilization can improve quality of maize grain, increase production of maize protein, chlorophyll content, leaf area index and harvest index.2. The results of economic optimum nitrogen fertilizer of super-high-yield summer maize and its effect showed that with the increased nitrogen levels, the production of summer maize was fist increased then decreased, under 300 kg·hm^-2 nitrogen application, the yield and incomes were the best, 11753.64 kg·hm^-2 and 13246.32kg·hm^-2、2063.33yuan·hm^-2 and 2364.84 yuan·hm^-2 respectively, the economic optimum nitrogen application is 255.4 kg·hm^-2, there were no economic benefits for summer maize when exceeded nitrogen application of 450 kg·hm^-2. Proper nitrogen application could increase the activity of nitrate reductase、sucrose phosphate synthase and glutamine synthetase. The proper nitrogen application to promote nitrogen metabolism is 300 kg·hm^-2, it also could promote the assimilation and accumulation of nitrogen. With the increase of nitrogen application, the nitrogen use efficiency of summer maize was decreased, with the nitrogen application of 300 kg·hm^-2, the means of two years’data of nitrogen use efficiency、agronomic efficiency and partial factor productivity were 16.12%、3.69 kg·kg^-1 and 41.67 kg·kg^-1 respectively. Considering the yield、economic benefits、nitrogen metabolism、accumulation of nitrogen、nitrogen use efficiency and so on, the proper nitrogen application were 255-300 kg·hm^-2 of super-high-yield summer maize.3. The research on effect of postponing N application on yield, nitrogen absorption and utilization in super-high-yield summer maize and its physiological bases showed that compared with conventional fertilizer application, postponing N application increased grain yield by 2.27%–5.33%. The N absorption proportion after silking stage was 40.30%–47.78% of the total, so it is important to provide maize plants with sufficient N in later growth stage for realizing super-high-yield. At later stage postponing N application could keep high leaf area index and chlorophyll content, promote N absorption and accumulation of super-high-yield summer maize at later stage, decrease N transfer efficiency in stem and leaf, increase activity of nitrate reductase、sucrose phosphate synthase、glutamine synthetase and content of free amino acids and soluble sugar in ear leaf at filling stage, and raise protein yield of summer maize. In comparison with conventional fertilizer application, the N fertilizer utilization rate and N fertilizer agronomy efficiency were increased by 1.88%–9.70% and 0.96–2.21 kg·kg^-1 respectively by postponing N application. The highest yield and nitrogenous fertilizer use efficiency were obtained by applying 30% of nitrogen fertilizer at seedling stage and trumpeting stage respectively and 40% of nitrogen fertilizer at silking stage.4. The studies on single application of base fertilizer （slow/controlled release N fertilizer）of super-high-yield summer maize showed that the plant N accumulation , yield, N fertilizer utilization rate and N fertilizer agronomy efficiency of CRNF improved by 6-7%, 3-4%, 5%, and 1.26-1.59 kg·kg^-1 compared with the conventional fertilizer application respectively; CRNF increased N absorption and utilization in the late growing periods, kept high chlorophyll content in leaf at filling stage, promoted grain filling and increased the content of maize kernel oil, crude protein, crude fat, protein yield, yield and nitrogen use efficiency. Applying CRNF was beneficial to realize single appli0cation of base fertilizer and the aim of simplify, high yield and high efficiency fertilization of super-high-yield summer maize.5. The research on effect of nitrogen fertilizer on yield and nitrogen absorption and utilization of two kinds of super-high-yield summer maize showed that the yield and incomes of Zhengdan 958 were the highest under low nitrogen condition, 12051.18 kg·hm^-2 and 1722.40 yuan·hm^-2 respectively, but the yield and incomes of Xundan 20 were the best under high nitrogen condition, 13166.00 kg·hm^-2 and 1343.92 yuan·hm^-2 respectively, the yield at three levels(N 0, 240 and 450 kg·hm^-2 )of Xundan20 increased by 9.90%、5.20% and 12.00% respectively, compared with Zhengdan958; From trumpeting stage to silking stage, the amount of assimilation and accumulation of nitrogen and absorption rate of nitrogen of Xundan 20 were higher than those of Zhengdan 958. At high N level, the absorption rate of nitrogen of Xundan 20 was also much more than that of Zhengdan958 at the later filling stage; The N use efficiencies, N use rate and N partial factor productivity of Xundan20 at high N level were significantly higher than those of Zhengdan 958, higher N application was beneficial to Xundan20 to get more production of protein. Considering the yield、nitrogen absorption、nitrogen efficiency and production of protein, Xundan20 is a nitrogen-efficient maize compared with Zhengdan 958.6. The results of the effect of nitrogen management on yield, quality, nitrogen absorption and utilization of summer maize in later harvest time showed that compared with local farmer habitual usage of N, postponing N fertilizer application and slow/controlled release N fertilizer could increase grain yield by 7.23%-9.52% and production of protein by 6.26%-10.73% in later harvest time; Compared with accustomed harvest, later harvest’s yield increased by 2.12% - 6.42%, production of protein increased by 1.11%-7.68% and N accumulation increased by 1.10%-3.18%;The stem and grain N accumulation increased in later harvest time, while the leaves and other organs is reduced;Postponing N application and slow/controlled release N fertilizer increased N use efficiency by 3.52%-6.87% and N agronomic efficiency by 0.82-1.60 kg/kg in later harvest time.