不同秸秆还田模式下水稳性团聚体有机碳的分布及其氧化稳定性研究

通过田间试验研究了不同秸秆还田模式条件下土壤团聚体分布、水稳性团聚体有机碳的含量及其氧化稳定性。结果显示:不同秸秆方式对各级别团聚体影响有差异,秸秆还田降低了微团聚体(<53μm)的含量,增加了大团聚体(>2000μm)和中微团聚体(250~53μm)的含量;在不同的还田模式下,总体看来小麦秸秆高留茬还田、玉米秸秆粉碎旋耕直接还田或覆盖还田对团聚体的分布影响较大。短时期内不同秸秆还田处理对团聚体稳定性影响较小。在小麦秸秆粉碎旋耕直接还田条件下,玉米秸秆粉碎旋耕直接还田更有利于大级别团聚体(>250μm)中有机碳的增加;在小麦秸秆不还田情况下,玉米秸秆粉碎旋耕直接还田或覆盖深松还田则有利于小级别团聚体中有机碳的提高。秸秆还田提高了较大团聚体(>2000μm和250~2000μm)有机碳的氧化稳定性。降低了较小团聚体(<53μm)有机碳的氧化稳定性。在同一小麦秸秆还田模式下,玉米秸秆粉碎旋耕直接还田有利于较大团聚体氧化稳定性的提高。相关分析表明:团聚体的平均几何直径(GMD)与250~53μm团聚体的有机碳含量和<53μm级别团聚体数量关系最密切。

The Distribution of Water-stable Aggregate-associated Organic Carbon and Its Oxidation Stability Under Different Straw Returning Modes

Field experiment was conducted to study the distribution and amount of water stable aggregate-associated organic carbon as well as its oxidation stability. The results indicated that straw returning reduced the amount of micro-aggregates(<53 μm) and increased the amount of macro-aggregates(>2 000 μm) and intermediate aggregate(250~53 μm); Overall, high wheat straw stubble returning, maize straw pulverization returning or mulching returning affected the distribution of aggregates significantly. Aggregates stability varied slightly among different straw returning modes in a short-term field experiment. Maize straw pulverization returning plus rotary tillage was more likely to increase the accumulation of macro-aggregate(>250 μm) associated organic carbon when wheat straw was pulverized and returned to soil directly. When no wheat straw was returned, maize straw pulverization returning and mulching returning both benefited the accumulation of micro-aggregate associated organic carbon. Straw returning increased the oxidation stability of organic carbon in comparatively large aggregate(>2 000 μm and 250~2 000 μm) and decreased the oxidation stability in small aggregate(<53 μm). Generally, under the same wheat straw returning modes, maize straw pulverization returning was in favor of the increase of the oxidation stability of organic carbon in comparatively large aggregate. Correlation analysis indicated that organic carbon of 250~53 μm aggregate and amount of <53 μm aggregate were two soil variables most closely related to soil aggregate geometric mean diameter(GMD).