Evaluating soil water matric pressure and sorptivity relationship as affected by some properties of a clay soil

Sorptivity (S) is the fundamental variable controlling the early infiltration process. Besides soil properties, soil initial water content (theta(i)) and (or) matric pressure (h(i)) are key factors determining extent of S. Assessment of interrelationship among S, h(i), and soil properties can provide a considerable insight into understanding the behaviour of dry soils to rainfall or irrigation water. This study was conducted to evaluate relationship between S and some selected soil parametric and morphometric properties within a range of h(i). Sixteen undisturbed soil samples (5 cm id, 5 cm length) were taken from the topsoil (0-15 cm) of a paddy soil with clay texture. Sorptivity was measured with a mini-disc infiltrometer on the samples equilibrated at h, ranging from -20 to -1500 kPa. A parameter (eta), representing the relationship between S and h(i), was introduced. Correlation analysis was conducted between eta and selected soil morphometric and parametric properties. Soil structure and clay content appeared the most important soil attributes influencing S-h(i) relation between -200 and -1500 kPa. The results provided a fundamental understanding on S-h(i)-soil properties interrelations in a clay soil. The methodology developed in this study can be used to evaluate S-h(i) relationship across different soils and scales.