Abstract:In order to study the carbon variation in cotton field under drip irrigation, the soil respiration rate and net photosynthetic rate were observed continuously during the cotton growth period using Li-8100A soil carbon flux automatic analyzer and LCpro+ photosynthetic apparatus. The results showed that the diurnal variation of soil respiration rates showed a unimodal curve with the peak at 16:00, while the diurnal variation of net photosynthetic rates in cotton field showed an alternating pattern of unimodal and bimodal curves. Both months showed a trend of increasing first and then decreasing, and the soil respiration rates and net photosynthetic rates reached the maximum in July. There were differences in soil respiration rates and net photosynthetic rates between different regions. The soil respiration rates were as follows inter-ridges > ridges > bare land, and the net photosynthetic rates was inter-ridges > ridges. The small area of cotton field showed carbon sinks throughout the growth period. From June to September, the total net carbon fixation in cotton fields was 2 203.7 C g/m2, and the carbon sequestration by photosynthesis was 2.67 times that of soil respiration.