For parameterization of the model, proportions of sand, silt and clay in the Halstow soil of the North Wyke site were obtained from Harrod & Hogan (2008), who used results from soil surveys of North Wyke. From these values field capacity and available water capacity were determined using the Saxton hydraulic properties calculator (Saxton & Rawls 2009) developed from statistical correlations between soil texture, soil water potential and hydraulic conductivity (Saxton et al. 1986). Although Halstow is normally better drained, all fields of the NWFP vary to some extent with compaction, and in this case the available water capacity for the Hallsworth series soil was lower than the Halstow soil (Table 1).