  Soil salinization and sodification can cause detrimental effects to soil
structure, with important implications to irrigated agriculture. Knowledge of
the extent to which degradation in soil structure due to salinization and
sodification is reversible is still lacking, however. The objective of our
study is to examine the effects of the history of solute composition on the
degree of reversibility in saturated hydraulic conductivity (Ksat). We
systematically investigate the effects of salinity (electrolyte concentration)
and sodicity (sodium adsorption ratio) on Ksat, for three soils of varying clay
content. The soil column experiments yielded hysteresis graphs, in which Ksat
does not go back to its original values after initial decay. We developed
indices to quantify the degree of Ksat degradation and reversibility, and found
that contrary to our expectations, high susceptibility to degradation does not
always correlate with low capability of rehabilitation. Measurements of soil
swelling helped us discern when degradation was mainly caused by swelling or
clay dispersion. Our findings underscore the need of understanding hysteresis
caused by salinity and sodicity, aiming at a better management of agricultural
soils for sustainable long-term use.
