Variation of soil compactness in 3 kinds of farmland soil profile in south Loess Plateau

chinois. 为了揭示黄土高原南部地区不同质地类型土壤剖面坚实度的变化及其与土壤含水率的定量关系，以黄痢v土、裸露在地表的粘化层耕作剖面为研究对象，定位观测其0~45 cm土壤坚实度与含水率的变化。结果表明，黄痢v土、裸露在地表粘化层耕作剖面的犁底层平均坚实度均大于耕层，犁底层平均坚实度较耕层分别高194.8%，87.3%，10.4%；剖面土壤质地越粘其平均坚实度越大；土壤坚实度与含水率呈负相关关系；土壤坚实度变化速率为0时，以上3种土壤剖面临界含水率分别为0.171 2，0.175 7，0.183 5；质地不同的土壤剖面坚实度时空变化特征有差异，其中黄疗拭0~20 cm土层土壤坚实度为350～500 kPa，受土壤含水率变化的影响较小；20~30 cm土层土壤的坚实度为500~1 400 kPa，不易受外界环境影响；30 cm以下土层土壤坚实度为700~1 600 kPa，受土壤含水率变化影响较大。v土剖面0~40 cm土层土壤坚实度为600~1 200 kPa，受含水率变化影响较大；40 cm以下土层土壤坚实度稳定在1 800 kPa左右。粘化层剖面0~15 cm土层土壤坚实度在2 000 kPa左右，受环境影响较大，15 cm以下土层土壤坚实度稳定在1 800 kPa，受含水率变化影响较小。

anglais. In order to observe soil compactness and water content dynamic change in 3 kinds of different texture soil profile (0－45 cm) in the south area of Loess Plateau, Huangshan soil, Lou soil, and Argic horizon were studied to find the law of soil compactness change and the relationship with soil water content. The result indicated the compactness in the plow-pan was great higher than that in the plow layer and the average compactness of plough pan was 194.8%, 87.3%, and 10.4% of cultivated horizon, respectively. The compactness increased with stickier of soil texture. Soil compactness and water content had negative correlation; different texture soil had a different variation velocity during the reduction process of soil water content; when the variation velocity was 0, three soil water content above was 0.171 2, 0.175 7, 0.183 5, respectively. Dynamic change of compactness was various with different soil texture. In Huangshan soil profile, soil compactness was 350-500 kPa in 0－20 cm, and the influence of soil water content changes was little; in 20-30 cm soil the compactness was 500－1 400 kPa and it was difficult bo be influenced by the environment, the compactness was 700－1 600 kPa under 30 cm depth, and could easily be affectde by rain water. In Lou soil profile, the soil compactness was 600－1 200 kPa in the layer of 0－40 cm and could be easily affected by the change of soil water content, the soil compactness under 40 cm depth was 1 800 kPa and had little change. In the Argic horizon profile, soil compactness was 2 000 kPa in the 0－15 cm and could be easily affected by environmental change; the compactness was 1 800 kPa under 15 cm and was not easily be affected by the change of soil water content.