Effects of different N rates on fate of N fertilizer and balance of soil N of winter wheat

The fate of N fertilizer and balance of soil N under winter wheat farming were studied using filed15N micro-plot. The results show that crop yield would not increase when the nitrogen application rate is above N 150 kg/ha. Apparent recovery efficiency and agronomic efficiency of nitrogen fertilizer are constantly decreased with increasing of rate of nitrogen fertilizer, while the trend of physiological efficiency is low-high-low. At lower N rate, more soil N is absorbed by winter wheat than that from fertilizer N, and the ratio of soil N absorption to fertilizer N absorption is decreased under high N application. After the harvest of winter wheat, 26.7%-40.6% of fertilizer N is resided in 0-100 cm, and 17.4%-24.8% of fertilizer N is lost. With increasing of nitrogen fertilizer application, the total balance of soil N is from deficiency to surplus, and NO-3-N in the root zone soil is from consuming nitrogen to cumulating nitrogen before seeding. There is similar trend between two wheat varieties.