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ABSTRACT
Some physical, chemical, and mineralogical properties of compacted and adjacent soil layers, which were selected from cultivated and virgin Willacy fine sandy loam soils in the lower Rio Grande Valley of Texas, were studied to attain a better understanding of the compacted zone and its development. Hydraulic conductivity measurements and field studies substantiated the presence of a hardpan layer, which was first encountered at a depth of 3
to 7 inches and ranged to a depth of 7
to 12 inches, at each of the five sites sampled. Clay content increased with depth, while sand content decreased. The fine (0.25 to 0.1 mm.) and very fine sand (0.1 to 0.05 mm.) fractions, for all samples, comprised at least 95% of the total sand and more than 60% of the total soil. Soil reaction (pH), organic matter content, cation-exchange capacity, exchangeable cations, and extractable silica, aluminum, and iron were determined. Extractable cementing materials were not found in important quantities in any of the layers. Mineralogical analyses of the samples showed that quartz and lesser amounts of feldspar composed the sand and silt fractions, while illite and poorly ordered, weathered micaceous materials dominated the clay fraction. No pronounced differences in the chemical and mineralogical properties of the hardpan layers as compared to the layers above and below the hardpan were found.
1 Contribution from the Texas Agr. Exp. Sta. and the Agronomy Department, The A & M College of Texas, College Station. Portion of a thesis submitted by the senior author as partial fulfillment of the requirements for the M.S. degree.
2 Former Research Assistant and Professors of Agronomy, respectively.
Received for publication December 13, 1960. Accepted for publication March 1, 1961.
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