We analyzed the particle size distribution of soil aggregates in 0-20 and 20-40 cm soil layers of rice-wheat rotation field based on a field plot test with two treatments, conventional straw returning (CK) and straw returning with the addition of straw decomposition promoting microbial inoculants (IT). We evaluated the water stability indices of soil aggregates (the number of soil water stable large aggregates R0.25, the average weight diameter MWD, and the geometric average diameter GMD), and measured the contents of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in the soil aggregates of ＜0.053, 0.053-0.25, 0.25-1, ＞1 mm. The results showed that: 1) The number of aggregates ＜0.053, 0.053-0.25, ＞0.25 mm in the 0-20 and 20-40 cm soil layers under IT decreased by 10.0% and 6.8%, increased by 3.0% and 5.7%, and 17.9% and 26.1% compared with CK, respectively. IT effectively increased R0.25, MWD, and GMD by 26.4%, 20.0%, 18.2% and 18.2%, 10.5%, 10.0% in 0-20 and 20-40 cm soil, respectively. 2) Compared to CK, the TP content of 0.25-1 mm aggregates in 0-20 and 20-40 cm soil under IT was significantly increased by 40.3% and 37.5%, respectively, without difference in TN and SOC contents. There was no significant difference in nutrient contents of the other aggregates between the treatments. The contents of SOC and TN in large aggregates (>0.25 mm) were higher than those in silty aggregates (<0.053 mm). Compared to CK, the cumulative contribution rates of SOC, TN and TP of <0.053 mm aggregates under IT were decreased in two soil layers. There was no significant difference in the nutrient cumulative contribution rates of 0.053-0.25 mm aggregates between treatments. The cumulative contribution rates of SOC, TN, and TP of large aggregates (>0.25 mm) under IT were 32.1%, 19.6%, 52.8% and 22.8%, 11.8%, 42.9% higher than those under CK in 0-20 and 20-40 cm soils, respectively. 3) The number of <0.053 mm aggregates was significantly negatively correlated with SOC and TP contents, while that of 0.053-0.25 mm aggregates was negatively correlated with nutrient content. The number of large aggregates (>0.25 mm) were significantly positively correlated with SOC, TN, and TP contents. In conclusion, straw returning with microbial-inoculant addition could promote the formation of soil macroaggregates (>0.25 mm), and improve the water stability of soil aggregates, increasing nutrient contents in soil macroaggregates, with the nutrients transferring from silty aggregates to macroaggregates.
采用大田小区试验,分析了常规秸秆还田(CK)和秸秆还田配施促腐菌剂(IT)两种处理下稻田0～20和20～40 cm土壤团聚体粒径分布,评估了土壤团聚体水稳定性(土壤水稳性大团聚体数量R0.25、平均重量直径MWD、几何平均直径GMD),并测定了不同粒径(＜0.053、0.053～0.25、0.25～1、＞1 mm)土壤团聚体中有机碳(SOC)、全氮(TN)、全磷(TP)的含量。结果表明: 1)IT处理＜0.053、0.053～0.25及＞0.25 mm团聚体数量在0～20和20～40 cm土层分别较CK下降10.0%和6.8%、提高3.0%和5.7%及17.9%和26.1%;与CK相比,IT有效提高了R0.25、MWD、GMD,在0～20和20～40 cm土层中分别提高了26.4%、20.0%、18.2%和18.2%、10.5%、10.0%。2)与CK相比,IT处理0～20和20～40 cm土层中0.25～1 mm粒级团聚体的TP含量分别显著提高了40.3%和37.5%,TN和SOC含量无显著差异;其他粒径各养分在两处理间无显著差异,大团聚体(＞0.25 mm)的SOC和TN含量高于粉黏团聚体(<0.053 mm)。不同土层IT处理<0.053 mm粒级团聚体的SOC、TN和TP累计贡献率较CK有所降低;0.053～0.25 mm粒级团聚体的养分累计贡献率与CK差异不显著;大团聚体(＞0.25 mm)的SOC、TN和TP累积贡献率在0～20和20～40 cm土层中较CK分别提高了32.1%、19.6%、52.8%和22.8%、11.8%、42.9%。3)土壤<0.053 mm粒级团聚体数量与SOC和TP含量呈显著负相关,0.053～0.25 mm团聚体数量与养分含量呈负相关,大团聚体(＞0.25 mm)数量与SOC、TN和TP含量呈显著正相关。综上,秸秆还田配施促腐菌剂可以促进土壤大团聚体(＞0.25 mm)形成,提高了团聚体水稳定性,增加了土壤大团聚体中养分含量,促使养分从粉黏团聚体向大团聚体转移。.
Keywords: microbial-inoculant; soil aggregate; soil nutrient; straw returning to the field.