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Applied and Environmental Soil Science
Volume 2012 (2012), Article ID 812561, 13 pages
http://dx.doi.org/10.1155/2012/812561
Research Article

Modelling Soil Water Retention for Weed Seed Germination Sensitivity to Water Potential

1Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada N1G 2W1
2Department of Soil Science, University of Manitoba, Winnipeg, MB, Canada R3T 2N2

Received 14 October 2011; Accepted 31 January 2012

Academic Editor: Keith Smettem

Copyright © 2012 W. John Bullied et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Soil water retention is important for the study of water availability to germinating weed seeds. Six soil water retention models (Campbell, Brooks-Corey, four- and five-parameter van Genuchten, Tani, and Russo) with residual soil water parameter derivations were evaluated to describe water retention for weed seed germination at minimum threshold soil water potential for three hillslope positions. The Campbell, Brooks-Corey, and four-parameter van Genuchten model with modified or estimated forms of the residual parameter had superior but similar data fit. The Campbell model underestimated water retention at a potential less than −0.5 MPa for the upper hillslope that could result in underestimating seed germination. The Tani and Russo models overestimated water retention at a potential less than −0.1 MPa for all hillslope positions. Model selection and residual parameter specification are important for weed seed germination by representing water retention at the level of minimum threshold water potential for germination. Weed seed germination models driven by the hydrothermal soil environment rely on the best-fitting soil water retention model to produce dynamic predictions of seed germination.