A Method for Obtaining a Continuous Measurement of Soil Moisture under Field Conditions.

A METHOD FOR OBTAINING A CONTINUOUS MEASUREMENT OF SOIL MOISTURE UNDER FIELD CONDITIONS A has been devised for making in situ under field conditions a continuous measurement of soil moisture. It consists of imbedding in the soil a standardized block of CaSO4 (plaster of paris). The moisture content of this material varies directly with that of the soil. Since the dielectric constant of plaster of paris is proportional to its moisture content, a measure of the conductivity of the block is a measure of soil moisture. Conductivity determinations are easily made by means of electrodes and a form of the Wheatstone bridge. This device measures soil moisture ranging from the wilting point to the field capacity or it is really a measure of the available water. It denotes the wilting point accurately. By knowing the wilting point and the available water, the total water content is thereby also known. The method possesses a surprisingly high degree of accuracy. --C~. J. BouYoucos AND A. H. MICK, Michigan Agricultural E~cperiment Station, East Lansing, Mich,