摘要: Step 2: Fitting of the Campbell Model The two-parameter power function model of Campbell (1974) is fitted to the water characteristic data (Chapter 22). A straight line is fitted to a plot of the natural log of volumetric water content (In (m³/m³)) versus the absolute value of the matric potential (ie ln (m) rather than ln (-m)) using linear regression. The natural log of water content is used as the response variable in the regression. The Campbell model is given by: