Estimation of the water balance of cultivated soils by mathematical models

In the last two decades a large number of mathematical models have been developed and used for simulating and predicting the unsaturated flow in non-cultivated and cultivated soils. It is the purpose of this paper to show the dynamics of these models and also to present a model that has been developed in the Laboratory of General and Agricultural Hydraulics and Land Reclamation of the School of Agriculture. The model is based on the numerical solution of the partial differential equation that describes the water movement in the unsaturated zone of a cultivated soil. It can predict the water regime of the soil profile taking into account only external to the soil system data (preceding irrigation, precipitation, meteorological data, etc.). Therefore it can constitute a very useful tool for irrigation scheduling by the managers of big cooperative irrigation networks. The model has been used to predict the water balance in several farms cultivated with cotton and sugar beets with very good results.