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Rapid Determination of Unsaturated Hydraulic Conductivity in Tilled and Untilled Loess Soil¹

ABSTRACT

A rapid method recently developed for determining moisture diffusivity and unsaturated hydraulic conductivity in undisturbed soil cores was employed to calculate the hydraulic functions of the upper layers of tilled and untilled loess soil. The results obtained with the new method compare well with results obtained by a field method. Diffusivity functions as influenced by tillage and depth were significantly different. Conductivities were highest in the 20–30-cm layer of untilled soil and were lowest in the same layer of tilled soil. The number of replicates necessary to evaluate the hydraulic functions with arbitrarily specified precision was calculated. For the soil under study, five to nine samples are needed, when upper and lower limits of the 95% confidence interval of diffusity means are defined not to be different more than by a factor of three.

¹ Contribution from the Institut für Pflanzenbau und Pflanzenzüchtung, Univ. of Göttingen, von-Siebold-Str. 8, 34 Göttingen, West Germany.

² Agronomist.

Received for publication April 21, 1976. Accepted for publication July 27, 1976.