INFLUENCE OF SALINITY AND SODICITY ON SOIL STRUCTURAL AND HYDRAULIC CHARACTERISTICS

An exchangeable sodium percentage (ESP) >15 is traditionally considere d to affect soil structural and hydraulic characteristics. Recent inve stigations show that both this critical value and the concept of criti cal threshold need reconsideration, because soil degradation often tak es place even at lower ESP in dilute solutions, and soil behavior at i ncreasing ESP appears to be a continuum. This study was carried out to analyze the response of two Sicilian Typic Haploxererts to ESP values up to 15, at a low cationic concentration. The investigation was carr ied out on aggregate stability, rating of soil shrink-swell potential, and both saturated and unsaturated hydraulic conductivity. The specif ic purpose was to verify if a critical ESP threshold exists, or if the hypothesis of a continuum behavior is more appropriate. The high-ener gy moisture characteristic technique was used for determining aggregat e stability, and Brasher's method for the shrinkage characteristic. Th e constant-head method was used for determining saturated hydraulic co nductivity, and the parameter estimation method based on one-step outf low experiments for unsaturated hydraulic conductivity. Almost linear relationships were found between the investigated soil properties and ESP, indicating no critical ESP threshold; furthermore, the results ob tained indicate that an effective hazard of soil quality degradation c an be forecast even in a 2 to 5 ESP range at a low cationic concentrat ion. This is a basic indication for irrigation management aimed to com bat and prevent degradation of soil quality.