耕作管理对潮土团聚体形成及有机碳累积的长期效应

【目的】研究黄淮海平原潮土区耕作管理对土壤水稳性团聚体形成及有机碳累积的长期效应,为提升潮土地力、推动农业可持续发展提供理论基础与技术支持。【方法】采集河南省封丘县中国科学院封丘农业生态实验站连续8年保护性耕作的不同处理原状土壤样品,分析测定土壤团聚体的数量、稳定性以及土壤和各粒径团聚体中的有机碳含量。【结果】与常规翻耕处理相比,长期免耕和间歇性翻耕使0—10 cm土层粗大团聚体和10—20cm土层细大团聚体的质量比例分别提高了63.4%和28.1%。秸秆还田主要提高了0—20 cm土层大团聚体的质量比例,平均提高率为3.0%。降低翻耕频率或秸秆还田处理,使不同土层团聚体的稳定性有所提升,前者使0—10 cm平均重量直径(mean weight diameter,MWD)和几何平均直径(geometric mean diameter,GMD)值分别增加了11.9%—31.6%和4.1%—13.7%;后者使0—20 cm MWD和GMD值分别增加了3.5%和4.5%,翻耕频率对团聚体稳定性的影响程度显著高于秸秆还田处理。在0—10 cm土层,各粒径团聚体的有机碳含量随翻耕频率的降低而提高,而秸秆还田对团聚体有机碳的影响可以深入0—20 cm土层。耕作方式耦合秸秆还田处理对团聚体特征的影响显著大于降低翻耕频率或秸秆还田处理。潮土有机碳积累的主要贡献来源于粗大团聚体和细大团聚体,通过降低翻耕频率,可以提高0—10 cm土层粗大团聚体和10—20 cm土层细大团聚体对潮土有机碳积累的相对贡献,提高率分别达49.2%和29.1%。【结论】长期免耕和间歇性翻耕结合秸秆还田能显著提高潮土大团聚体的数量及其稳定性,通过提高大团聚体对土壤有机碳积累的相对贡献,可以增加潮土碳累积量。

The Long-Term Effect Research of Various Tillage Managements on the Soil Aggregates and Organic Carbon in Fluvo-Aquic Soil

【Objective】The long-term effects of various tillage managements on aggregation and organic C accumulation were investigated for promoting Fluvo-aquic soil quality in the North China plain.【Method】In this paper, undisturbed soils were sampled, which lasted for 8 years under conservation tillage at the State Experimental Station of Agro-Ecosystem in Fengqiu. The mass and stability of aggregates, and organic C concentration in bulk soil and aggregates were measured to evaluate the impact of tillage managements.【Result】Compared with conventional tillage, no-tillage and intermittent tillage markedly enhanced the mass proportion of large macro-aggregate in 0-10 cm layers and small macro-aggregate in 10-20 cm layers by 63.4% and 28.1%, respectively. In 0-20 cm layers, the mass proportion of macro-aggregate was increased by 3.0% under straw incorporation compared to that without straw returning. Tillage frequency reduction or straw incorporation improved the stability of aggregates, and the Mean Weight Diameter (MWD) and Geometric Mean Diameter (GMD) of the former in 0-10 cm layers were enhanced by 11.9%-31.6% and 4.1% -13.7%, respectively, while those of the latter in 0-20 cm layers were increased by 3.5% and 4.5%, respectively. Tillage frequency reduction and straw managements increased the organic C concentration of aggregates in 0-10 cm and 0-20 cm layers, respectively. Moreover, tillage methods coupled with straw managements had more significant effects on soil aggregates than single tillage frequency reduction or straw returning. The large and small macro-aggregates made more contribution to the accumulation of organic C in Fluvo-aquic soil, and the relative contribution from large macro-aggregate in 0-10 cm layers and that from small macro-aggregates in 10-20 cm layers could be enhanced by 49.2% and 29.1% respectively, through tillage frequency decrease.【Conclusion】No tillage and intermittent tillage combined with straw management could markedly accelerate soil aggregation. By enhancing the contribution of macro-aggregates to organic C accumulation, C sequestration in Fluvo-aquic soil would be also accelerated under conservation tillage.