关键词: 氮肥, 棉花（Gossypium spp.）, 小麦（Triticum aestivum L.）, 轮作, 生产效益, 秸秆还田

Abstract: In order to study how to reduce nitrogen fertilizer input and improve the comprehensive benefits of cotton fields under the dual cropping system of cotton （Gossypium spp.） and wheat （Triticum aestivum L.） rotation in the cotton region of the Yangtze River Basin, five nitrogen fertilizer dosage treatments were set up in the experiment, which were low nitrogen （N1,50% of N3）, relative low nitrogen（N2,75% of N3）, medium nitrogen（N3, pure nitrogen in the cotton season and wheat season were 180.0 and 150.0 kg/hm², respectively）, high nitrogen（N4, 125% of N3） and rich nitrogen （N5, 150% of N3）. The effects of different nitrogen fertilizer application rates on the growth process, agronomic traits and yield traits of wheat and cotton and cotton fiber quality were analyzed, and the economic benefits, land use efficiency and production efficiency of different treatments were analyzed. The results showed that the total production cycle of cotton-wheat rotation was about 344 days, and it was feasible to develop cotton wheat rotation in the cotton region of the Yangtze River Basin. The effective number of ears, grains per ear and yield of wheat among different nitrogen fertilizer application rates first increased and then decreased with the increase of nitrogen fertilizer application rate. Based on two years of experimental results, when the nitrogen fertilizer application rate was high （N of 187.5 kg/hm²）, the yield of wheat was highest. There were significant differences in cotton plant height, number of bolls per plant, seed cotton yield, and lint yield among different nitrogen fertilizer application amounts. When the nitrogen fertilizer application amount was high nitrogen （225.0 kg/hm²）, the seed cotton yield was the highest. In the annual production of cotton and wheat, the total output, production efficiency, net profit, return rate and input-output ratio showed a trend of first increasing and then decreasing with the increase of nitrogen fertilizer application, and the maximum value was reached when the fertilizer application level was high nitrogen（N4）. The total production cycle and soil utilization rate increased with the increase of nitrogen fertilizer application amount.

Key words: nitrogen fertilizer, cotton（Gossypium spp.）, wheat（Triticum aestivum L.）, rotation, production efficiency, straw returning