Gamma ray attenuation was evaluated as a means of determining soil bulk density. Experiments were conducted using clay, silt, and sandy loam soils wherein samples were compacted to uniform densities at various moisture contents. We determined the attenuation characteristics of dry soil to be independent of soil texture while being significantly different from that of water. Comparison of gamma density measurements with known soil sample densities indicated that the gamma gauge provided reliable measurement of soil bulk density, provided that the effect of soil moisture on attenuation was accounted for and the manufacturer-prescribed calibration procedure was followed daily. Further, we determined a relationship whereby correction can be made for deviation from the prescribed separation distance between the gamma source and detector.

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Published in Transactions of the ASAE, v. 35, issue 1, p. 17-26.

© 1992 American Society of Agricultural Engineers

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The investigation was conducted in connection with a project of the Kentucky Agricultural Experiment Station and was funded in part by a grant from the USDA Cooperative States Research Service.

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This document is published with the approval of the Director of the Agricultural Experiment Station as Paper No. 89-2-138.