To explore the effect of under-mulch-drip irrigation on canopy photosynthesis, canopy structure and yield formation of hybrid cotton planted in Xinjiang, an experiment with limited drip irrigation was carried out under field condition. The results were as follow: limited drip irrigation caused water deficiency in cotton field, reduced canopy apparent photosynthesis (CAP) and leaf area index (LAI); under this treatment, the canopy respiration rates (CR) and the ratio of CR to total CAP were higher in fully flowering stage but fell rapidly in full boll stage. The limited drip irrigation increased leaf mean foliage inclination angle (MFLA), transmission coefficient for diffuse penetration (TCDP) and transmission coefficient for radiation penetration (TCRP), with low light interception rate; On the other hand, excessive drip irrigation promoted the over-rapid growth of hybrid cotton, canopy leaf source capacity (CLSC) and high dry matter accumulation. But CR increased rapidly at late growth stage, and CAP was at its minimum level, result in low yield. In the case of hybrid cotton, under appropriate irrigation treatment, CAP was higher, and LAI increased sharply. It maintained at a higher LAI level at late stage, so it had a steady growth and optimal leaf physiological function which led to higher yield. Studies showed that the suitable amount of drip irrigation for Zhaofeng-1 in South Xinjiang was 3 000-4 125 m 3/nm 2. Its corresponding yield was 7 714.3-8 289.5 kg/hm 2. The ideal canopy photosynthesis characteristic and canopy structure targets of hybrid cotton were discussed.
