Salt Distributions in Cracking Soils and Salt Pickup by Runoff Waters

Detailed measurements were made of the levels and distributions of salts present in representative soil profiles and fields and associated tailwaters in the Imperial Valley of California. The findings showed that the potential salinity-pickup hazard may be greater in this valley that is dominated by cracking soils than classical theory would predict. Salts that would otherwise be “isolated” in seedbeds or leached downward during irrigations are more “exposed to” and “picked up by” the runoff water than previously recognized as a result of the flow of the irrigation water throughout the beds and horizontally in the topsoil via the extensive network of cracks and fractures that form in the cracking soils. As a result, the pattern of salinity within the beds of such soils is one-dimensional, rather than the expected, classical two-dimensional pattern. Salt content in the tailwater associated with cracking soils was higher and sustained over longer periods of time than in the case of noncracking soils.