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

【Objectives】Nitrogen fertilizer having been widely used in agricultural production, many studies illustrated the efficiency of nitrogen, however, few studies showed the nitrogen accumulation and transport at the anthesis and maturity stages of winter wheat in high-yielding system. A field experiment was conducted to determine effects of different management patterns on uptake, distribution and fate of nitrogen in winter wheat. We indicated impacts of optimizing nitrogen and water management on N uptake-soil residues-loss, explored nitrogen accumulation and transport at the anthesis and maturity stages, and identified fate of nitrogen.【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 the characteristics and nitrogen utilization by measuring soil and plant samples.NH+4-N and NO-3-N in the fresh soil samples were analyzed using continuous flow analysis (TRAACS 2000) in laboratory. 15N in the soil and plant were determined using the Delta plusXP.【Results】Under the experimental conditions, the differences in grain yields and nitrogen uptakes of wheat between the optimized and conventional treatments are significant. Compared to the conventional treatment, the grain yield and nitrogen uptake under YH are increased by 35.23% and 34.39%, respectively. The rate of 15N utilization of the conventional treatment (18.19%) is significantly lower than that of the optimized treatment (34.81%). The amounts of accumulated nitrogen in the crop aboveground organs and the amounts of transferred nitrogen to grain from soil nitrogen are significantly higher than those from fertilizer nitrogen. Therefore, soil nitrogen is the main nitrogen source of wheat. The nitrogen in seed mostly comes from the accumulation before the flowering, and the contribution rates of transporting nitrogen by organs of the conventional and optimized patterns are 81.65% and 62.14% respectively. After the wheat harvest, the contents of nitrate and 15N in 0-100 cm soil of the optimized pattern are significantly lower than those of the conventional pattern. The 15N contents under CT with soil depth increase at the first and then decrease, with the accumulation peak in 40-60 cm. The amount of nitrogen fertilizer is as follows: soil residual crop uptake loss. The residual nitrogen rate in soil of the conventional pattern is up to 69.33% which is significantly higher than that of the optimized pattern (39.17%).【Conclusions】It can be reached that high levels of grain yield and use efficiency of nitrogen with nitrogen controlled at around 139 kg/ha. Thus, we conclude that less nitrogen and reasonable water stress not only raise the efficiency of nitrogen fertilizer but also increase food production.