Effects of Straw Incorporation on Soil Organic Carbon Density and the Carbon Pool Management Index under Long-Term Continuous Cotton

The objective of this experiment was to study the effects of residue management on soil organic carbon density and the carbon pool management index under continuously cropped cotton (Gossypium hirsutum L.) in China’s Xinjiang Province. The experiment included the following nine treatments: (i) annual straw incorporation during 5, 10, 15, 20, 25, and 30 years of continuous cotton and (ii) annual straw removal during 5, 10, and 15 years of continuous cotton. The results showed that the total organic carbon, labile organic carbon, the labile organic carbon/total organic carbon ratio, soil organic carbon density, and the carbon pool management index all increased with time in the straw incorporated treatment, but decreased with time in the straw removed treatments. Soil carbon concentrations, which are naturally low in the Xinjiang Region, had not reached saturation after 30 years of continuous cotton with straw incorporation.