Abstract:In order to investigate the stability of soil structure and the distribution characteristics of organic carbon in different soil depths (0~10cm, 10~20cm,…, 90~100cm) under long-term conventional tillage and no-tillage conditions, mixed soil samples and undisturbed soil samples collected from no-tillage and conventional tillage treatments were designed to measure soil structure and soil organic carbon content. The results indicated that with the increase of soil depth, the contents of aggregates with diameter of 0.5~2.0mm and greater than 2.0mm were gradually decreased, while other particle agglomerates were increased. No-tillage treatment could improve the large aggregates (greater than 0.5mm) content, and significantly improve the stability of soil structure, the effect of depth was more than 60cm. With the increase of soil depth, soil organic carbon and active organic carbon content were increased firstly and then decreased, and then trended to be stable. Soil carbon and active organic carbon of no-tillage treatment in 0~80cm soil layer were higher than that of conventional tillage. With the increase of soil depth, soil aggregates organic carbon content was decreased, while organic carbon content of large aggregates was higher than other size aggregates. No-tillage was more conducive to increase soil organic carbon content of different size aggregates under 0~40cm soil depth. With the decrease of soil aggregates, soil active organic carbon content was decreased. Compared with conventional tillage, except 0.053~0.250mm size aggregate, no-tillage increased active organic carbon content in 0~20cm soil layer of various aggregates. With the increase of soil depth, the contribution rate of organic carbon to soil total organic carbon in different size fractions showed the trend of decreasing first, then increasing and then decreasing. In different aggregates, contribution rate of organic carbon of aggregates with diameter greater than 2.0mm and less than 0.053mm in the 0~100cm soil layer was lower than those of other size aggregates. In 0~20cm, 30~40cm and 90~100cm soil layers, accumulation contribution rate of different aggregates organic carbon of no-tillage treatment was higher than that of conventional tillage.
