秸秆还田对麦粱两熟农田土壤团聚体特征的短期效应

冬小麦—夏高粱种植系统作为一种新型农业两熟制系统，是山西省杂粮可持续发展的一项有效措施。为阐明该种植系统农田土壤团聚体粒级分布及稳定性对秸秆还田量的短期响应，试验基于麦粱种植系统，分析了不还田（CK）、半量还田（HR）和全量还田（WR）对土壤团聚体粒级分布特征和稳定指数的影响。结果表明:秸秆还田后，能够显著降低0—30 cm土层 > 10 mm和 < 0.25 mm粒级机械稳定性团聚体含量，增加0.25～2 mm各亚粒级水稳性大团聚体含量，同时显著降低了土壤团聚体破坏率和不稳定团粒指数（p < 0.05）；全量秸秆还田后较半量秸秆还田对农田土壤团聚体特征改善效果更为明显，但对10—20，20—30 cm土层改善效果逐渐减弱；全量还田相比半量还田，土壤机械稳定性团聚体平均重量直径、几何平均直径和大团聚体（> 0.25 mm）含量分别显著降低了12.2%，23.0%和5.3%，并显著提升了水稳性团聚体几何平均直径和大团聚体（> 0.25 mm）含量，降低了水稳性团聚体分形维数（p < 0.05）。此外，土壤团聚体稳定性与有机碳含量、孔隙度、含水量和作物产量呈显著正相关（p < 0.05）。综合表明，全量还田在短期年限内能够显著提高土壤团聚体稳定性，是改善晋中区麦粱两熟农田土壤团粒结构和增加作物产量的有效措施。

Short-Term Responses of Soil Aggregate Characteristics to Different Annual Straw Incorperation Rates in Winter Wheat-Summer Sorghum Cropping System

As a new type of agricultural double cropping system, winter wheat-summer sorghum planting system is an effective measure for the sustainable development of cereal grains in Shanxi Province. In order to elucidate the short-term response of grain-size distribution and stability of soil aggregates to straw application in this cropping system in farmland, based on the winter wheat-summer sorghum cropping system, the effects of treatments of no crop residue returning (CK), 50% (HR) and 100% (WR) on grain-size distribution characteristics and stability index of soil aggregates were analyzed in this study. The results showed that straw returned to field could significantly reduce the mechanical stability of aggregate (> 10 mm and < 0.25 mm) in 0—30 cm soil layer, significantly increase the contents of 0.25～2 mm water-stable aggregates. At the same time, the PAD and E_LT were significantly reduced (p < 0.05). The effect of WR compared HR treatment on improving the characteristics of soil aggregates in farmland was more obvious, but the improvement effects in the soil layers of 10—20 cm and 20—30 cm gradually declined. The MWD, GMD and R_0.25 of mechanics-stable soil aggregate decreased significantly by 12.2%, 23.0% and 5.3%, respectively; the GMD and R_0.25 of water-stable aggregates increased significantly, and the values of water-stable aggregates D (p < 0.05) reduced under WR treatment compared with those under CK. In addition, the aggregate stability was positively correlated with organic carbon, porosity, water content and crop yield (p < 0.05). It showed that the WR treatment is an effective measure to improve the soil aggregate characteristics and increase crop yield by significantly increasing the stability of soil aggregates in winter wheat-summer sorghum cropping system field in Jinzhong area within a short period of time.