Abstract

Hamid Reza Fooladmand

Soil moisture characteristic (SMC) curve is a basic soil property. Since its direct measurement is costly and time-consuming, an alternative to measurement is to estimate this property indirectly, using the more easily available soil properties. These methods are called pedotransfer functions (PTFs). Point PTFs estimate the water content of the soil at different matric potentials. For this study, twenty soil samples from the topsoils (A horizons) were selected from different locations in Fars province, South of Iran, and SMC curve of each soil was measured with the combination of hanging column for matric potentials of 0 (saturated soil moisture content), 3, 6, 9 and 12 kPa and pressure plate methods for matric potentials of 30, 100, 500, 1000 and 1500 kPa. Also, the particle size distribution curve of each soil was measured and the percentages of clay, silt and sand, and the geometric mean particle-size diameter of each soil was determined. Then, three PTFs were derived based on clay or sand fraction of the soil or geometric mean particle- size diameter, saturated soil moisture content and bulk density for point estimation of SMC curve. To evaluate the proposed PTFs another five independent soils were used. The results showed that, the PTFs for point estimation of SMC curve based on clay content were appropriate for soils with clay, silty clay and silty clay loam textures, and the PTFs based on sand content were appropriate for soils with loam and sandy loam textures.