Objective  Aggregate distribution and organic carbon stability of farmland soil at Minqin Oasis under different methods of tillage were studied for improvements on the soil erosion eradication and agriculture sustainability in the area.

  Methods  Taking advantage of the ongoing fixed position monitoring program at Minqin Oasis and utilizing a virgin land in the area as control (CK), 4 tilling methods including no-tilling (Tn), less-tilling (Tm), deep-loosening (Ts), and autumn turning-over (Tf) were performed to determine their effects on the aggregate composition and organic carbon stability of the soil.

  Results   (1) In terms of soil aggregates, the tested tillage significantly increased the proportion of aggregates containing particles larger than 0.25 mm in the soil. Among them, Tm yielded 9.39% higher proportion than Tn, 11.38% higher than Ts, 6.09% higher than Tf, and 35.41 higher than CK in 0-20 cm soil, and 13.74% higher than Tn and 38.65% higher than CK in 20-40 layer. At the same time, Tm, Ts, and Tf significantly increased the mean weight diameter (MWD) and geometric mean diameter (GMD). (2) In terms of soil organic carbon stability, all 4 tilling methods significantly increased the content and cumulative mineralization of organic carbon in aggregates of different sizes in the soil layers. However, Tn resulted in greatest organic carbon content among them. It significantly increased carbon content over Ts, Tf, and CK by 18.58%, 39.53%, and 58.40%, respectively, in the soil at a depth of 0-20 cm, and 40.08%, 22.84%, and 60.93%, respectively, in the 20-40 cm layer. And the content decreased with reducing particle size and increasing depth of soil. In addition to agglomeration smaller than 0.25 mm, the cumulative mineralization of organic carbon treated by Tn was significantly higher than CK. Meanwhile, the tillage significantly reduced the organic carbon contribution proportion in soil by microaggregates smaller than 0.25 mm, as Tn, Tm, Ts, and Tf significantly reduced it by 32.89 %, 49.37 %, 26.61 %, and 38.88 %, respectively, over CK in 0-20 cm layer of the soil.

  Conclusion  Tillage promoted the formation and stability of aggregates and also improved the carbon stability in soil. The less-tilling Tm and the no-tilling Tn minimized mechanical damage to the soil while increased the organic carbon content of large aggregates in surface and tillered soil. Tn was especially conducive to the carbon fixation, and Tm to the stability of soil. Thus, those two methods were recommended for farming in the region.