耕作措施对土壤水稳性团聚体及有机碳分布的影响

通过9a不同耕作的定位试验,研究了深松、旋耕、免耕和传统耕作4种耕作措施对关中塿土小麦-玉米轮作条件下土壤水稳性团聚体及有机碳垂直分布的影响。结果表明,与传统耕作相比,深松、旋耕、免耕措施均提高了0～40cm土层中>2mm和0.25～2mm大团聚体含量、团聚体有机碳贡献率和团聚体平均重量直径,而传统耕作相应地增加了0～40cm土层中0.053～0.25mm微团聚体和<0.053mm粘砂粒含量及其有机碳贡献率。同时深松、旋耕、免耕措施提高了各土层总有机碳和耕层0～10cm所有级别团聚体有机碳含量,相比较而言,深松的作用效果更大。秸秆还田进一步提高了各土壤层次上总有机碳和所有级别团聚体的有机碳含量及大团聚体的形成与稳定。在玉米秸秆不还田的条件下,隔年深松比连年深松更有利于0～30cm大团聚体形成及总有机碳和各级别团聚体有机碳的积累。

Effects of Tillage Practices on Water-stable Aggregation and Aggregate-associated Organic C in Soils

A field experiment was conducted on the Guanzhong plain to study the effects of tillage on the distribution of water-stable aggregates and aggregate-associated organic C.Four tillage practices were compared:sub-soiling,rotary tillage,no-tillage,and conventional tillage.The soil type was a Lou soil and the cropping system was a winter wheat-summer maize rotation.The results showed that compared to conventional tillage,nine years of sub-soiling,rotary tillage,or no-tillage increased the mass of macroaggregates(i.e.,>2 mm and 0.25～2 mm size classes),the contribution of macroaggregate-associated organic C to total soil organic C,and the mean weight diameter in the 0～40 cm depth.In comparison,the mass of the microaggregate(i.e.,0.053～0.25 mm)and minera(li.e.,<0.053 mm)fractions and the contribution of these size fractions to total soil organic C were greater in the conventional tillage treatment.Sub-soiling,rotary tillage,and no-tillage also increased total soil organic C at all depths and the aggregate-associated organic C of all size classes at the 0～10 cm depth.The largest increase in aggregate-associated organic C was in the sub-soiling treatment.The return of crop residue to the soil increased the total soil organic C content as well as the aggregate-associated organic C content of all aggregate size classes at the 0～40 cm depth.The return of residue also facilitated the formation and stabilization of macroaggregates.When maize residue was not returned to the soil,sub-soiling every other year had better effects than sub-soiling every year.Specifically,sub-soiling every other year increased total soil organic C as well as aggregate-associated organic C in each size class.Compared to annual sub-soiling,sub-soiling every other year also increased the formation and stability of macroaggregates at the 0～30 cm depth.