The problem of the coupled flow of heat and moisture vapour in soil is modelled using ideas of lumped, time delay prameters, to simulate the many non-linearities which occur in soil. Such ideas have been used previously in the construction of Aggregated Dead Zone models, which have been used with considerable success by field workers describing solute flow in rivers. The corresponding differential equations for soil are presented and it is shown how their simple parameterisation have certain advantages for experimenters over more traditional approaches. Under the assumption that field workers can obtain direct measurements of moisture and heat flux, and also temperature and moisture content at two depths, it is shown how the descriptors of the model can be derived. The specific examples given are based on purely harmonic measurements made by experimenters and it is shown how Fourier analysis may be applied in a simple way to deal with more realistic experimental situations. Finally, it is indicated how the full spectrum of results may be used to describe how the descriptors vary with time and hence with moisture content and temperature.