Clipping Date Effects on Soil Water and Regrowth in Crested Wheatgrass

Abstract

Although extensive work has evaluated plant response to season of defoliation, few studies have evaluated the influence of season of defoliation on soil water depletion, amount of regrowth, and total seasonal biomass production. This 5-year study evaluated the effect of clipping date and yearly climatic variation on soil water depletion, amount of regrowth, and total seasonal forage production. Timing of clipping significantly (P?0.05) affected soil water depletion patterns. Clipping at the early vegetative stage had little effect on soil water potential unless soil water potentials were below-0.03 MPa. In mid June soils beneath plants defoliated during the boot stage were consistently wetter than soils beneath undefoliated plants. However, total seasonal soil water depletion was usually similar among treatments by the end of the growing season. Phenology and the amount of standing crop present when defoliation occurred were significantly (P?0.05, R2 = 0.877) correlated with regrowth. Date of defoliation also significantly (P?0.05) affected total production in wet years. Total seasonal forage production on plots clipped during the boot stage was generally lower than on plots clipped during the vegetative or late-flowering stages