陕西关中地区农田土壤物理状态初探

摘要

为了反映现代人为强度作用下农田土壤质量的演化趋势,对陕西关中不同地区土壤容重和坚实度做了调查与研究.结果显示,关中地区农田土壤容重底层显著大于表层,表层0～10 cm土壤容重平均值为1.00g/cm3,属于正常范围;10～20 cm平均容重为1.40 g/cm3,大于1.30 g/cm3达到紧实程度标准以上的土壤样品数占到88%;20～30 cm土壤平均容重值为1.61 g/cm3,容重高于1.40 g/cm3属于很紧实土壤样品占到96%,达到该土壤质地类型的极限容重1.60g/cm3以上样品占到52%,该土层成为限制作物根系延伸的土层;30～40 cm平均容重值也为1.60g/cm3,达到很紧实以上水平,但是达到极限容重以上的样品数为44%.土壤坚实度在0～25 cm范围内急剧增加,25 cm以下保持在1 600 kPa左右,对作物生长产生了一定水平的机械障碍.同时分析得知,土壤坚实度与土壤容重呈极显著的正偏相关关系,而与含水量只是呈不显著的负偏相关关系,说明本试验条件下土壤坚实度增大的原因主要是由于土体密实化所引起的.试验结果证实,关中地区农田土壤仅在10 cm以上表层土壤维持着对作物生长无明显物理障碍状态,其下土层密实化问题不仅严重而且非常普遍,土壤密实化导致了坚实化,制约着作物根系延伸,深层密实化和坚实化具有很强的隐蔽性,应给予足够的重视.深耕松土是改善关中农田土壤物理状态的可行措施.%In order to reveal the variation tendency of farmland soil quality under the influence of human activity,we investigated the soil bulk density and soil compactness in different districts in Guanzhong area. The results showed that the soil bulk density in deep layers was significantly higher than that in top soils, with an average of 1.00 g/em3.However, in the 10 ～ 20 cm layer the samples exceeding 1.30 g/cm3 accounted for 88％ of the overall, with an average of 1.40 g/cm3. In the 20 ～ 30 cm layer the values averaged 1.61 g/cm3, and the samples exceeding 1.40 g/cm3 accounted for 96％ of the overall. So, this layer was defined to confine plant roots in a large extent. Similarly, the average value of soil bulk density was 1.60 g/cm3, and 44 ％ of the samples were higher than the standard ( 1.60 g/cm3 ). In the 0 - 25 cm layer the soil compactness increased sharply, however it kept at 1 600 kPa under 25cm in the soil, probably having restricted the growth of plants. Through partial correlation analysis, it was clear that soil compactness, significantly, was positively related to soil bulk density, negatively related to soil water content. It indicated the reason why soil compactness increased was due to soil bulk density. In this experiment only the top 10cra - layer soil was fit for planting,and deep layers were universally compacted, which posted a severe problem in root extending. What's more, the problem under deep soil layers was invisible, thus we must pay great attention to it. It seemed that deep plough and scarification were useful methods for improving farmland soil physical status in Guanzhong.