Influence of Crested Wheatgrass on Soil Water Repellency in Comparison to Native Grass Mix and Annual Spring Wheat Cropping

Crested wheatgrass (Agropyron cristatum (L.) Gaertn.) is a common introduced grass in the Canadian prairies, but concerns remain about its possible long-term effects on soil quality, and its influence on soil water repellency (SWR) has not been determined. The long-term (24 yr) effects of crested wheatgrass on soil water repellency (SWR) in comparison to seeded native grasses and annual cropping were determined for a clay loam soil in southern Alberta, Canada by measuring SOC concentration and SWR using soil hydrophobicity (SH) and soil water repellency index (RI) methods. The cropping treatments were crested wheat grass, seeded native grass mix, continuous wheat, and wheat-fallow rotation, each with fertilized (nitrogen) and non-fertilized sub-plots, replicated four times. Mean SOC concentration, SH, and RI in samples of surface soil were similar (P > 0.05) for crested wheatgrass and seeded native grass mix; and did not support our hypothesis (seeded native grass mix>crested wheatgrass). Mean SOC was significantly greater for seeded perennial grasses than annual crops by 1.7 to 2 times and SH by 2.1-2.5 times, which supported our hypothesis, but RI was similar among treatments. As expected, nitrogen fertilization significantly increased SOC concentrations, but the effects on SH and RI were undetectable. A strong positive correlation occurred between SOC concentration and SH (r=0.92), but not for RI (r=0.10). Our findings suggested that SWR was similar for crested wheatgrasses and seeded native grass mix. The SWR as measured using SH was greater for seeded perennial grasses than annual cropping, but was similar using RI.