Abstract: To promote the rational application of nitrogen fertilizer in winter wheat after rice stubble, the effects of nitrogen application rate (0, 150, 225, 300 kg·hm^-2, expressed as N₀, N₁₅₀, N₂₂₅, N₃₀₀) on nitrogen recovery, residue, loss and grain yield were examined using field ¹⁵N tracer technology. The results showed that with the increases of application rate, nitrogen accumulation from different sources significantly increased while nitrogen recovery significantly decreased. The accumulation of basal nitrogen in plants reached the peak during overwintering stage to jointing stage, while the accumulation of topdressing nitrogen peaked between jointing to flowering stage. At maturity, nitrogen accumulation of the top fertilizer was higher than that of the base fertilizer. Plant nitrogen accumulation from soil under N₁₅₀ was higher than that from nitrogen fertilizer, but with an opposite tendency under N₂₂₅ and N₃₀₀. With the increases of nitrogen application rate, the residual nitrogen in the 0-100 cm soil layer in the maturing stage significantly increased, while the residual nitrogen ratio in the 60-100 cm soil layer gradually increased. In the whole growth period of wheat, both nitrogen loss and loss ratio were positively correlated with nitrogen application rate. The nitrogen loss of base fertilizer reached the highest during sowing to overwintering stage, while the nitrogen loss of top fertilizer was at the peak from jointing to flowering period. Taking grain yield into consideration, N₂₂₅ treatment was the proper application rate for winter wheat after rice stubble, with grain yield being 6735 kg·hm^-2, and the nitrogen fertilizer recovery rate, soil residue rate and loss rate being 42.6%, 34.0% and 23.3%, respectively.

Key words: wheat after rice stubble, nitrogen uptake, nitrogen residue, nitrogen loss, grain yield