SHORT-TERM EFFECTS OF SURFACE-APPLIED GYPSUM ON REVEGETATED SODIC BENTONITE SPOILS

The high clay content and saline-sodic characteristics of bentonite mi ne spoils result in an environment that is not conducive to sustainabl e plant growth. Use of wood residue amendments have enabled revegetati on of these materials; however, sodic conditions persist or worsen, th reatening the long-term sustainability of these revegetated lands. Gyp sum, 56 Mg/ha, was surface applied to these revegetated ecosystems to evaluate its effectiveness in ameliorating the spoil sodicity under a natural precipitation environment. The gypsum treatment significantly reduced the exchangeable Na and the exchangeable Na percentage of the 60-cm spoil profile 3 yr after treatment. The gypsum amendment also si gnificantly increased the spoil-water storage in the 60-cm spoil profi le. Gypsum treatment resulted in a significant increase in the spoil e lectrical conductivity; however, this increase did not detrimentally a ffect the vegetation. Surface-applied gypsum amendment effectively ame liorated the revegetated bentonite mine spoil sodicity under natural r ainfall conditions in a semiarid environment.