Straw returning coupled with nitrogen fertilization increases canopy photosynthetic capacity, yield and nitrogen use efficiency in cotton

Nitrogen (N) fertilization plays a pivotal role in canopy photosynthetic capacity and yield formation of cotton (Gossypium hirsutum L.), but the interaction effects with consecutive straw returning remain poorly understood. A field experiment was conducted (2015?2018) to examine the effects of N fertilization (0, 75, 150, and 300 kg N ha-1) coupled with or without barley and cotton straw supplementation on soil nutrient status, cotton canopy photosynthetic capacity, seedcotton yield, and nitrogen use efficiency (NUE) in Yancheng, China. N fertilization coupled with straw addition enhanced most cotton growth traits, showing higher canopy apparent photosynthesis rate, leaf area index, leaf N content, specific leaf area, and boll density, and progressively increased seedcotton yield annually. In 2018, straw addition increased seedcotton yield by 7.5 %, 9.6 %, 12.1 %, and 4.1 % under 0, 75, 150, and 300 kg N ha-1, respectively, compared to corresponding treatments of straw removal. The highest increase in seedcotton yield and NUE under 150 kg N ha-1 combined with straw addition was due to the greatest improvements in soil fertility, canopy photosynthetic capacity, and N uptake by cotton. In addition, the results suggested that approx. 33?44 % of chemical N fertilizer reduction would not affect seedcotton yield with straw addition. Our results demonstrated that straw returning combined with 150 kg N ha-1 had benefits on improving soil nutrient status, canopy photosynthetic capacity, seedcotton yield, and NUE of cotton.