A LABORATORY PROCDURE FOR DETERMINING THE FIELD CAPACITY OF SOILS

Abstract

Direct detn. of field capacity requires moisture sampling of freshly irrigated and gravity-drained soil. Since this is tedious and sometimes inconvenient, a number of laboratory procedures have been devised for its indirect detn. In the method described herein small blocks of screened soil were placed on a porous ceramic cell, satd. with water, and drained under 25 cm. Hg tension. The moisture retained by each drained soil was plotted in relation to the field capacity of the same soil detd. directly in the field. A curvilinear relation was found to exist between these determinations over the range from 4 to 32% field capacity. Descriptions are given of the detn. procedure, and the design of the tension control equipment.