Effects of cultivation on organic carbon fractionation and aggregate stability in Xinjiang oasis soils
垦殖对新疆绿洲农田土壤有机碳组分及团聚体稳定性的影响

Soil organic carbon is an important indicator of soil quality, and labile organic carbon fractions play an important role in soil quality development. In this study, fractionation of labile soil organic carbon was performed to evaluate the effects of cultivation practices on the changes of organic carbon and aggregate stability in soils of the desert area. The results showed that organic carbon content significantly increased in 1-5 years after the low organic matter natural soil was converted to cotton field, with an mean annual increase of 0.65 g kg-1 or increased by 76%-286%. Soil organic C attained relative balance after 5 years of cultivation. Soil labile organic carbon (LOC) and light fraction organic carbon (LFOC) increased significantly in 1-5years, with an average increment of 72%-99%, but declined after 5 years of cultivation. Particulate organic carbon (POC) significantly increased in 1-10 years of in cultivation, with a maximum increase of 275%, and declined after 10 years of cultivation. Water\|stable aggregates (WSA) in soil increased significantly with cultivation, up to 75% as compared with the original natural soil in 0-20 years. These results indicate that cultivation has an important influence on soil organic carbon pools of the oasis farmland. Long\|term of cultivation of the desert soil tends to decrease labile organic carbon and subsequently may potentially cause degradation of soil quality, which merits further attention.