FIELD-TEST OF SOLUTION FLOW MODELS IN A HETEROGENEOUS IRRIGATED CROPPED SOIL

Data obtained from a controlled irrigation experiment in a citrus grove are compared with results obtained from simultaneous water and salt flow models considering water uptake by the trees. In the models, spatial variability in soil hydraulic properties has been taken into account by using a single dimensionless scaling parameter which allows the range of the soil water retentivity h(θ) and hydraulic conductivity K(θ) functions to be approximated with a probability of about 0.95. Measured data of water content profiles were obtained with the aid of the neutron probe method. Saturated paste extracts of disturbed soil samples were used for the measured salt profile data. Variability in the water and salt content observations is expressed in terms of the 95% confidence limits (CL) of the measurements made in six replications at each of the three experimental treatments. An irrigation period of 7 months was simulated and compared each year. The comparisons between models and experiments are based on average values, on ranges of CL of field data, and on simulated results computed with highly probable ranges of soil hydraulic properties. The results suggest that for estimating field values of water content (θ) and salt distribution profiles with approximate ranges of K(θ) and h(θ) at a given probability, the models have been sufficiently developed. Copyright 1979 by the American Geophysical Union.