PAM和草类根系对荒坡侵蚀劣地紫色土微团聚体的影响

为探讨PAM(聚丙烯酰胺)和草类根系对侵蚀劣地土壤的改良效果,试验以该环境的紫色土为研究对象,设置了空白对照(CK)以及单施PAM、单植草类、"狗牙根+PAM"、"三叶草+PAM"4个试验处理类别,6个月后测定了土壤微团聚体组成,分析了土壤微团聚体分布、结构及分形特征。结果表明,1)各试验处理的大粒径微团聚体含量增加,小粒径的则减少;2)各试验处理的MWSSA(平均重量比表面积)、分散系数和分散率均显著减小(各指标最小值分别为CK的0.30、0.15和0.60倍),MWD(平均重量直径)、团聚状况和团聚度均显著增大(各指标最大值分别为CK的1.17、1.49和1.28倍);3)各试验处理的微团聚体分形维数均减小;4)GY-PAM1(狗牙根+液施PAM,浓度:30 g/m~3)土壤的各项微团聚体结构指标均优于其他试验处理,表现出较好的抗侵蚀性;5)"草类+PAM"的根系指标均优于单植草类,平均根长密度(RLD)和d(直径)≤0.2 mm径级分别是影响该紫色土结构稳定性和抗侵蚀性的主要因子和关键径级。

Impacts of polyacrylamide and grass root systems on micro-aggregates of purple soil in barren hillside badlands

In order to explore the improvement effects of polyacrylamide (PAM) and grass roots on soil in badlands,the composition,distribution,structural and fractal characteristics of soil micro-aggregates in purple soil were measured after six months exposure to various treatments,including blank control (CK),polyacrylamide on the soil surface,grass planting alone,"Cynodon dactylon+PAM" and "Trifolium repens+PAM".The results indicated that the proportion of large particle size micro-aggregates of each experimental treatment increased while the proportion of small particle size micro-aggregates decreased,compared to CK.Hence,the mean weight soil specific area (MWSSA),dispersion coefficient and dispersion rate of experimental treatments significantly decreased (The minimum values were 0.30,0.15 and 0.60 times those of CK,respectively).The mean weight diameter,aggregation states and degree of aggregation of each experimental treatment significantly increased (The maximum values were 1.17,1.49 and 1.28 times those of CK,respectively).The fractal dimension of micro-aggregates in experimental treatments also decreased.All the structural parameters of microaggregates in soils of treatment GY-PAM1 (C.dactylon planting and liquid application of 30 g/m3 polyacrylamide) were superior to the other treatments and this treatment showed greater reduction in erodibility.The root system parameters of "grass+PAM" were better than those of grass-planting alone.The total root length and the root length in the diameter (d) class d≤0.2 mm were the major factor and critical diameter class affecting structural stability and erodibility reduction of purple soil in barren hillside badlands.