A comparison of three methods of soil water content determination

Abstract

In forestry the need to manage plantations on a sustainable site-specific basis requires the understanding and management of any growth limiting factors. Soil water regime is a factor considered to be of prime importance with respect to explaining differences in tree growth. In research studies measurement of soil water content is carried out on a regular basis and due to theft and vandalism, soil water sensing equipment cannot usually be left on site. Other rapid methods to determine soil water content therefore have to be found. The ThetaProbe and Speedy Moisture Testèr were compared as alternative measures of soil water content determination in the top 10 cm of the soil to the more traditional gravimetric method. These methods were tested in KwaZulu-Natal on two contrasting soils in terms of clay content, organic carbon content and soil water content. Regression analysis performed to compare the two different methods with the gravimetric method as a reference, indicated that they were similar on a soil specific basis at the P < 0,001 level of significance. With calibration, they were found to be equally suitable for the purpose of taking the measurements. Results and problems encountered are discussed for each method.