Layer Thickness Changes in a Clay-Rich Soil in Relation to Soil Water Content Changes
1967
Jamison, V. C. | Thompson, G. A.
Changes in soil water content and layer thickness of a soil with clay-enriched horizons will depend upon the rooting depth and seasonal growth characteristics of the plant cover, as well as the nature of the soil itself. Soil anchors fitted with sleeves were turned to different depths in Mexico silt loam under bluegrass and alfalfa. Elevation measurements were made at each location with respect to benchmarks consisting of 3.7-meter, sleeve-fitted rods driven into the soil. Soil water measurements were made with a neutron meter. High corre'ations were found between water content and layer thickness of the clay-rich layers. Alfalfa (Medicago sativa) proved to be much more effective in water removal from the claypan and deep subsoil than bluegrass (Ppoa pratensis). Disregarding expansion in the surface layer due to freezing, the greatest shrinking-swelling effects were in the claypan. About one-fourth of the magnitude of soil water change in the claypan of Mexico silt loam was manifested as a change in soil layer chiekness.
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