Effects of long-term N and P fertilization with different rates on Zn concentration in grain of winter wheat

【Objectives】Wheat is one of the staple food crops in northwestern China,and mainly grown in calcareous soil with low available Zn, and grain Zn concentration is consequently low and hardly meets with the nutritional demands of Zn from local people. Therefore, improving wheat grain zinc concentration is of great significance for human health.N and P applications influence the uptake and utilization of Zn by winter wheat. Based on a long-term (2004-2013), a two-year study was conducted during 2011-2013 to investigate the effects of long-term different N and P fertilization rates on Zn concentration of winter wheat grain to lay a theoretical foundation for effective regulation of grain zinc nutritional quality of winter wheat, and propose practical measures for optimizing nitrogen, phosphorus fertilizer management in winter wheat production. 【Methods】 The long -term field experiment is located in the experiment station of the Northwest AF University, Yangling, Shaanxi Province. The experiments were arranged in completely randomized block design with four replications. The local winter wheat cultivar of Xiaoyan22 was used as test crop. The experiment of long-term different N fertilization rates, is compossed of five N rates of 0, 80, 160, 240 and 320 kg/ha, and the experiment of long-term P fertilization is composed of five P application (P2O5) rates of 0, 50, 100, 150 and 200 kg/ha. Winter wheat samples were collected in 2011-2013 years to test grain yield and its component factors, N, P and Zn concentrations of grain, straw and glume, and to calculate N, P and Zn contents in the aerial plant part. 【Results】Both the grain Zn concentration and Zn uptake in the aerial plant part are positively correlated (P0.01) with the N application rate, when the rate is less than 320 kg/ha. By adding each 100 kg/ha N, the grain Zn concentration is increased by 4.0 mg/kg, and the Zn uptake increased by 36.4 g/ha. There is positively correlation (P0.01) between the grain N concentration and N in the aerial plant part. Each increase N 1 g/kg grain of leads to by 2.0 mg/kg of increase in Zn. Each increaseof 100 kg/ha N uptake in the aerial plant part leads to its Zn increase by 142.9 g/ha. However, when the P application rate is less than 200 kg/ha, the grain Zn concentration is observed to be negatively (P0.01) correlated with the P application rate and the grain P concentration, with each 100 kg/ha P application rate increase, the grain Zn concentration is found decreased by 9.2 mg/kg, and with each 1 g/kg grain P concentration increase, the grain Zn concentration is decreased by 24 mg/kg. The Zn uptake in the aerial plant part is not significantly correlated with the P application rate and P uptake in the aerial plant part. 【Conclusions】 For a better balance between the grain yield and grain zinc concentration, application rates of N and P are suggested to be controlled respectively within N 160-240 kg/ha and P2O5 50-100 kg/ha in this area.