Predicting the saturated hydraulic conductivity of compacted subsoils using the non-similar media concept
Predicting the saturated hydraulic conductivity of compacted subsoils using the non-similar media concept
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DOI：
10.1016/j.still.2004.11.010
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发表时间：
2005-12-01
影响因子：
6.5
通讯作者：
Miyazaki, T
中科院分区：
文献类型：
--
作者：
Nakano, K;Miyazaki, T
人们普遍认为，饱和导水率是由土壤孔隙的微形态决定的，而不仅仅是总孔隙度或干体积密度。然而，一些研究人员报告说，底土饱和导水率的下降只是与土壤孔隙度的减少或干容重的增加有关。根据已发表的文献中的这些认识和我们的初步野外调查，我们认为，在频繁耕作的持续干扰下，表层土壤孔隙的微形态会受到破坏，而底层土壤往往会被压实，而土壤孔隙的微形态没有发生严重的变化。因此，我们通过将土壤分为耕作层和压实层来研究土壤饱和导水率与干容重的关系。本研究的目的是利用非相似介质概念(NSMC)模型来描述饱和导水率与干容重之间的关系，该模型能够预测不同干容重值土壤的饱和导水率。研究区域位于日本崎玉县Tone河附近，根据日本耕作土壤分类(联合国粮农组织/联合国教科文组织)，该地区的土壤被归类为单一棕色低地土壤。两个地点选择了表层土壤季节性耕作，而底层土壤保持原样，另一个地点也进行了表层土壤季节性耕作，但进行了超深耕作(1na耕作深度)。在室内测定了不同深度原状土芯的饱和导水率和干容重。NSMC模型只有在样本间土壤质地相同的情况下才被仔细应用。用Kozeny-Carman和Campbell建立的著名的传统方程与NSMC模型进行了比较。NSMC模型成功地预测了压实地基中的饱和导水率。另一方面，NSMC模型不适用于耕作的表土和深耕的底土。相同干密度条件下，耕层土壤和深耕土壤的饱和导水率始终低于压实土壤。Kozeny-Carman方程和Campbell方程在预测地基饱和导水率时均失败。NSMC模型计算结果表明，无扰动压实条件下，地基土的饱和导水率与其干容重有很好的相关性。(C)2005 Elsevier B.V.保留所有权利。
It is widely recognized that saturated hydraulic conductivity is dominated by the micromorphology of soil pores rather than by the merely total porosity or dry bulk density. Nevertheless, some researchers are reporting that the decrease in saturated hydraulic conductivity of subsoil is simply associated with the decrease in soil porosity or increase in dry bulk density. Based on these understandings in published papers and on our preliminary field investigation, we assumed that micromorphology of soil pores in topsoils is subjected to be destroyed with continuous disturbance by frequent tillage while subsoils tend to be compacted without serious changes of micromorphology of soil pores. Thus, we focused on finding the dependence of saturated hydraulic conductivity on dry bulk density by separating the soils into tilled layer and compacted layer. The objective of this study was to describe the relationship between saturated hydraulic conductivity and dry bulk density using a theoretical model, the non-similar media concept (NSMC) model, capable of predicting saturated hydraulic conductivities of soils with different values of dry bulk densities. The study area was located near the Tone River in Saitama Prefecture, Japan, where the soils were classified into Haplic Brown Lowland Soils according to the Classification of Cultivated Soils in Japan (Eutric Fluvisol according to FAO/ UNESCO). Two sites, where the topsoils were seasonally tilled while the subsoils were sustained as it is, and another site where the topsoil was seasonally tilled, too, but extra deep tillage (1 na tillage depth) had been done, were chosen for the measurements. The saturated hydraulic conductivities and dry bulk densities of undisturbed soil cores from different depths were measured in the laboratory. The NSMC model was carefully applied only when the soil textures were the same among samples. The well-known conventional equations formulated by Kozeny-Carman and by Campbell, were used to compare the applicabilities with the NSMC model. The NSMC model succeeded in predicting the saturated hydraulic conductivities in the compacted subsoils. On the other hand, the NSMC model was not applicable to the tilled topsoils and to the deeply tilled subsoil. The saturated hydraulic conductivity of tilled topsoils and deeply tilled subsoil was always lower than that of compacted subsoils at the same dry bulk densities. The Kozeny-Carman and Campbell equations both failed in the prediction of saturated hydraulic conductivity in subsoil. It was concluded that the saturated hydraulic conductivity of subsoils under compaction without extreme disturbance is well related with its dry bulk density by the NSMC model. (C) 2005 Elsevier B.V. All rights reserved.