In Alberta, Mapfumo et al. quantified soil water patterns from grazed and ungrazed perennial and annual forages and to evaluate the ability of Versatile Soil Moisture Budget (VB2000) model to simulate soil water content on these systems. Soil water was affected by forage species more than grazing treatments. The average daily actual evapotranspiration rates were 3-4 mm d-1 in both years. Bulk densities were generally greater for grazed compared to ungrazed treatments, especially for the old grass high input pasture treatment. Soil water contents were mostly within the field capacity and wilting point range throughout the season; however, at the end of the growing season soil water was lower than wilting point. Simulations of volumetric soil water for selected forage x grazing treatment combinations during the evaluation year of 2000 indicated that modeling efficiencies of 0.30, 0.24, 0.19, and 0.24 for grazed alfalfa (Medicago sativa), ungrazed alfalfa, grazed annual and ungrazed annual, respectively. However, when the soil water simulations for all treatments were combined, the overall modeling efficiency was 0.43. It is important in VB2000 applications that site-specific calibrations be conducted, preferably on a smaller scale to ensure minimal spatial variability in soil attributes.
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