
%0 Journal Article
%A Henderson, B. L. 
%A Bui, E. N. 
%T An improved calibration curve between soil pH measured in waterand CaCl<emph type="8">2</emph>
%J Soil Research
%D 2002/12/10
%V 40
%N 8
%P 1399-1405
%K soil acidity
%R https://doi.org/10.1071/SR01098
%U https://www.publish.csiro.au/paper/SR01098 
%X A new pH water to pH CaCl2 calibration curve was derived from data pooled from 2 National Land and Water Resources Audit projects. A total of 70465 observations with both pH in water and pH in CaCl2 were available for statistical analysis. An additive model for pH in CaCl2 was fitted from a smooth function of pH in water created by a smoothing spline with 6 degrees of freedom. This model appeared stable outside the range of the data and performed well (R2 = 96.2, s = 0.24). The additive model for conversion of pHw to pHCa is sigmoidal over the range of pH 2.5 to 10.5 and is similar in shape to earlier models. Using this new model, a look-up table for converting pHw to pHCa was created. 
