Objective: It is of great significance to explore the effects of different irrigation methods and fertilization measures on soil carbon balance in cotton field during cotton growth season in arid region, and to compare the effects of different management practices on soil carbon sequestration intensity in cotton field. Method: Two-factor experiments with two irrigation methods and four fertilizer treatments were conducted during cotton growth period. Drip irrigation and flood irrigation were arranged as two different irrigation methods and organic manure (OM), N P K fertilizer (NPK), combined application of NPK fertilizer and organic manure (NPK+OM) and no fertilization (CK) were arranged as four fertilizer treatments. Soil respiration rate in cotton field was measured by LI-8100 automated soil CO 2 efflux system and root contribution of soil respiration was detected by root exclusion method. Soil carbon sequestration intensity in cotton field under different irrigation methods and fertilization measures was analyzed by calculating net ecosystem productivity (NEP). Result: Under the conditions of different irrigation methods and fertilization measures, seasonal variation of cropland soil respiration rate showed an increase at first, then followed a declining trend with air temperature change. Soil respiration rate reached a peak in mid-July and then reduced to the minimum in mid-October after cotton harvest. Soil carbon emission under drip irrigation was larger than that under flood irrigation, and under the same irrigation condition, the soil carbon emission with NPK+OM treatment was the highest, then with OM, CK, NPK in turn. The ratio of root respiration contribution to soil respiration was fluctuated between 36.38% and 58.74% under drip irrigation method, whereas between 33.73% and 52.03% under flood irrigation method. Root respiration contribution was the highest at the boiling stage. During the whole growth period, the root respiration contribution under drip irrigation and flood irrigation was averagely 48.05% and 44.31%, respectively. The order of net primary productivity (NPP) of cropland was NPK+OM > NPK > OM > CK under different irrigation methods in the whole season. Cotton field was carbon sink under different management practices in the whole season, and the intensity of carbon sink under drip irrigation was stronger than that under flood irrigation. Under the same irrigation condition, the order of the intensity of carbon sink was NPK+OM > NPK > OM > CK. Under the condition of interaction between irrigation method and fertilization measure, the carbon sink intensity was the strongest under drip irrigation method and NPK+OM. Conclusion: In arid region, cotton production using cropland management measures, such as water saving technology of drip irrigation under mulch, combined application of NPK fertilizer and organic manure and straw returning, could not only increase soil organic carbon content, fertilize the soil fertility and improve cotton yield, but also promote to fix carbon and reduce discharge.
