Effects of different management patterns on uptake, distribution and fate of nitrogen in summer maize

【Objectives】 A field experiment was conducted to determine effects of different management patterns on uptake, distribution and fate of nitrogen in summer maize. We indicated impacts of optimizing management pattern onN uptake-soil residues-loss, explored nitrogen accumulation and transport at the anthesis and maturity stages, and identified fate of nitrogen. The study can provide theoretical and technical supports for local agricultural development. 【Methods】 Two management patterns i.e., conventional pattern (CT) and optimized pattern (YH) in nitrogen and water management were designed through establishing 15N-micropolt experiments in the field. We analyzed characteristics and nitrogen utilization by measuring the soil and plant samples. Soil samples were extracted with 1 mol/L KCl, and analyzed for NH+4-N and NO-3-N using continuous flow analysis (TRAACS 2000) in laboratory. The samples were dried and sieved through a 0.15 mm mesh. They were taken for determination of 15N using the Delta plusXP. 【Results】The differences of grain yield and total nitrogen uptake between the optimized and conventional patterns are significant. As to the conventional pattern, the grain yield and nitrogen uptake are 12% and 10% lower than those of the optimized patterns, respectively. The rate of 15N utilization of the conventional patterns (20.81%) is significantly lower than that of the optimized patterns (32.54%). The contents of accumulated nitrogen in the crop aboveground organs and the contents of transferred nitrogen to the grain of soil nitrogen are significantly higher than those of fertilizer nitrogen. About half of nitrogen content in seed comes from the accumulation after the flowering. The transport contribution rates by organs of the conventional and optimized patterns are 57.73% and 45.15%, respectively. The nitrate and marked 15N accumulation amounts in the soil surface at the period of the anthesis under the conventional patterns are higher than those under the optimized patterns, and after the harvest the 15N content of the conventional pattern with soil depth is increased for the first and then decreased, with the accumulation peak in 20-40 cm. The residual nitrogen rate in soil of the conventional pattern is up to 56.18%. The fate of nitrogen fertilizer is as follows: soil residual loss crop uptake. As to the optimized treatment, the fate of nitrogen fertilizer is as follows: soil residual crop uptake loss. 【Conclusions】It can be reached high level of grain yield and efficiency of nitrogen with nitrogen controlled at around 185 kg/ha. Thus, less nitrogen and more times of fertilization at late growth stage not only raise the efficiency of nitrogen fertilizer but also increase food production.