Improvement of Salt-affected Soils by Deep Ploughing : — Part 1: Plot Field Tests in a Saline Soil (Solonchak) Region —

概要

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A method was investigated for improvement of salt-affected soils in regions where a sufficient amount of rainfall to percolate into subsoil occurs in summer. A coarse layer is provided in the subsoil by deep tillage, making soil clods to cut off the capillary rise from groundwater. This paper deals with plot test fields constructed by hand in a saline soil (solonchak) region. The results showed that the deep tillage to the subsoil was beneficial for the improvement of the solonchak soil. Where the Ap horizon (topsoil) alone was tilled, the vegetation was poor because the capillary rise was not perfectly cut off. Reduction of the pH from about 9.5 to 8.5 was obtained. The EC value decreased from about 0.5 dSm−1 to 0.2 dSm-1. From these results, we determined that the tillage should be deeper to intercept the capillary rise at the subsoil.