渭北旱塬区秸秆覆盖还田对土壤团聚体特征的影响

为了研究不同秸秆覆盖还田量对半湿润易旱区土壤团聚体分布状况和稳定性特征的影响,在渭北旱塬设置三种覆盖还田量(SM1:13 500 kg/hm2、SM2:9 000 kg/hm2、SM3:4 500 kg/hm2),以不覆盖为对照进行定位试验,研究了秸秆覆盖还田对土壤容重、土壤有机碳、土壤团聚体数量、大小及分形维数的影响。结果表明,秸秆覆盖还田后,土壤容重随秸秆覆盖还田量的增加而减小,0~20 cm土层土壤容重较对照降低了2.00%~5.28%(P>0.05);土壤总有机碳含量随着土层深度的增加而递减,在0~20 cm土层,土壤总有机碳含量较对照显著提高10.82%~23.93%。10~30 cm土层,SM2处理下>0.25mm机械稳定性团聚体含量、平均重量直径(MWD)和几何平均直径(GMD)均高于SM1、SM3,各处理间差异不显著;在0~40 cm土层,各处理>0.25 mm土壤水稳性团聚体、MWD和GMD较CK均有不同程度提高,但差异不显著。各处理均可提高0~30 cm土层土壤团聚体稳定性,其中SM2团聚体分形维数D最小,其次为SM1、SM3。可见,秸秆覆盖还田可促进土壤团聚体的形成,提高团聚体的稳定性,以SM2覆盖还田的效果最佳。

Effects of straw mulching treatment on characteristics of soil aggregates in Weibei dryland

In order to evaluate the effects of straw mulching on the aggregation and stability of soil aggregates in Weibei dryland of Shaanxi,different amounts of straw mulch(SM1: 13 500 kg/hm2,SM2: 9 000 kg/hm2,SM3: 4 500 kg/hm2,CK: 0 kg/hm2) were selected to conduct an locating experiment.We studied the effects of straw mulching on soil bulk density,organic carbon,aggregates number,size distribution and fractal dimension for four years(2007—2010).The results indicated that,after maize harvest,straw mulching treatments decreased the soil bulk density and soil total organic carbon at 0～20 cm soil layer.Compared with the CK,the soil bulk density decreased varying from 2.00%～5.28%(P>0.05),while the soil total organic carbon increased by 10.82%～23.93%(P<0.05),and decreased with deeper layer.The dry sieving results showed that macro-aggregate content(R0.25),mean weight diameter(MWD) and geometric mean diameter(GMD) in SM2 were higher than in other treatments at 10～30 cm soil layer,and had very significant difference with CK.Wet sieving results showed that macro-aggregate content,MWD and GMD in all treatments were higher than CK,but not significantly.All treatments improved the aggregate stability at 0～30 cm soil layer,and the fractal dimension(D) showed that SM2 had best aggregate stability.Therefore,the straw mulching treatments increased the aggregation and the stability of soil aggregates,ans SM2 had the best result in this experiment.