Patterns and simulation of soil water under different grazing management systems in central Alberta

- Authors: E. Mapfumo, D. S. Chanasyk, and V. S. Baron
  
  Date: 2003
  
  Journal: Canadian Journal of Soil Science
  
  Volume: 83
  
  Number:
  
  Pages: 601-614
  
  Summary of Methods: 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.
  
  Article Summary / Main Points: None
  
  Vegetation Types:
  
  MLRA Ecoregions:
  
  Agrovoc Control Words: Riparian zones Rangelands Wildlife
  Article Review Type: Refereed
  
  Article Type: Experimental Research
  
  Keywords: evapotranspiration, forage, model calibration, model evaluation, versatile soil moisture budget model, alberta
  
  Annotation: Each paddock was approximately 1.2 ha and was seeded to one of three forages: alfalfa (Medicago sativa), an annual, and a mixture of meadow bromegrass (Bromus riparius) and alfalfa. The annual pasture in 1999 was Italian ryegrass (Lolium multiflorum) and a mixture of winter triticale and oats (Avena sativa) in 2000.,An adjacent 30-year old high-input old grass perennial pasture composed of quackgrass (Elytrigia repens), smooth bromegrass (Bromus inermis), and Kentucky bluegrass (Poa pratensis) represented the common grazing management practice in the area. The grazing management system was a rotational system. In 1999, seasonal stocking rates for annual, alfalfa, old grass pasture, and meadow bromegrass/alfalfa were 2.1, 4.5, 5.1, and 6.1 head/ha, respectively. In 2000, seasonal average stocking rates were 4.9, 6.0, 5.0, and 7.7 head/ha, respectively. Forage within each exclosure was defoliated using clippers as the cattle were rotated through the treatment.

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