A model for estimating soil moisture deficits under cereal crops in Britain:1. Development

Abstract

SUMMARY: A new and detailed model, involving meteorological, crop and soil variables, is proposed to provide daily estimates of moisture deficits in soils under cereal cropping in Britain. The model incorporates developments in the calculation of potential evapotranspiration specifically for cereal crops. Four processes of loss of water are considered, namely drainage, evaporation of free water from the crop canopy, evaporation from the soil surface and transpiration by the crop. Thus the model is applicable at all stages of the cropping cycle. Above-ground and root system development of the crop are modelled and available and extractable water capacities of a wide range of soils are estimated. Thus the demand for water and its availability are varied with crop species, stage of development and soil type as well as with meteorological variables.The calculation of water losses is not dependent on arbitrary assumptions about the division of losses between the four processes considered or between different horizons of the soil.Extreme simplicity of input data requirement has been maintained. The model has been programmed in FORTRAN, and is compatible with Meteorological Office data archives.