SUMMARYThe two‐parameter model In φ= a+b ln θis widely accepted in the literature as providing a good fit to the soil moisture characteristic for a wide variety of soil types. This model is examined and it is shown that the parametersaandbare not independent, and hence that the SMC may be represented by a one‐parameter model with little loss of accuracy. Thus it is possible to define the SMC from one paired measurement of soil water content against potential. Because this single paired measurement is all that is required it also avoids the necessity of classification of the soil type–indeed it may provide an additional means of soil identif