种草和施用聚丙烯酰胺对荒坡紫色土抗剪和抗蚀性能的影响研究

为探究种植草类和施用聚丙烯酰胺(PAM)对荒坡紫色土抗侵蚀性的影响,尤其是对其抗剪和抗蚀性能的影响,选取狗牙根和三叶草进行盆栽试验,设计了对照、单植草类、单施PAM和复合措施(“草类+PAM”)4类处理开展研究,测定了根系指标和土壤理化性状指标,计算了土壤的抗剪强度指标和抗蚀性指标。结果表明,狗牙根和三叶草根系均能显著降低土壤容重、提高土壤孔隙度和有机质含量(P<0.05),有效增强土壤的抗剪和抗蚀性能;施加PAM能有效促进上述草类各径级根系的生长,显著改善土壤的微结构(P<0.05),尤其是非毛管孔隙度(单施PAM为CK的1.15~1.31倍),提高土体抗剪强度及内摩擦角φ,增大粒径>0.25 mm、>0.5 mm的水稳性团聚体含量、平均重量直径和几何平均直径等抗蚀性指标;PAM对荒坡紫色土抗剪和抗蚀性能的增强效果存在最优浓度;草类根系对土壤抗剪性能的影响较抗蚀性能明显,能显著提高土体的抗剪性能(P<0.05),尤其是增大土壤粘聚力;PAM对土壤抗蚀性能的影响较抗剪性能明显,能显著促进土壤团聚体大颗粒的形成和小颗粒的减少,显著提高土壤团聚度和改善土壤团聚结构等(P<0.05);较单一措施,“草类+PAM”对荒坡紫色土抗剪和抗蚀性能的增强效果最为明显,其中狗牙根与30 g·m^-3的PAM混施时效果最优;0

Effect of planting grasses and adding polyacrylamide on the shear performance and erodibility-resistance of purple soil in barren hillsides

This study investigated the effect of planting a grass-legume mixture and adding polyacrylamide (PAM) on the shear performance and erodibility-resistance of purple soil in a pot trial. Cynodon dactylon and Trifolium repens were chosen as the plant species. The experiment had four treatments: CK, bare soil; GL, planted in C. dactylon and T. repens; PAM, a single application of PAM; and GL+PAM. Root parameters, basic physical and chemical properties, shear strength (including its constituent components), and erodibility-resistance parameters were measured. The roots of C. dactylon and T. repens significantly reduced soil bulk density, and increased soil porosity and soil organic matter (P<0.05), and improved the soil shear performance and erodibility-resistance. PAM effectively promoted the growth of the root system, significantly improved the soil microstructure (P<0.05), especially the non-capillary porosity, which after the single application of PAM was 1.15-1.31 times that of CK. PAM also increased the shear strength and internal friction angle φ, the erodibility-resistance parameters of water stable aggregates >0.25 mm (WSA_0.25), water stable aggregates >0.5 mm (WSA_0.5), mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates. The improvement in shear performance and erodibility-resistance obtained using optimal concentration of PAM would be expected to stabilize purple soil in barren hillsides better. The main effect of roots in the GL pots was the improvement of soil shear performance (P<0.05), especially cohesion. PAM had a stronger effect on erodibility-resistance because of the formation of larger aggregates, thus significantly improving the degree of aggregation and soil aggregate structure (P<0.05). Compared with GL or PAM alone, GL+PAM produced the most obvious improvement in the shear performance and erodibility-resistance of purple soil in barren hillsides. The best performance was obtained with C. dactylon planting and addition of polyacrylamide at 30 g·m^-3 soil. The critical root diameter conferring shear performance and erodibility-resistance of soil was 00.2, RSAD_0.2), root length density (RLD) and root volume density (RVD) are key indexes of the contribution of roots to soil shear performance.