Applicability of Darcy’s law for predicting irrigation head: what are the limits?

Abstract

Modelling soil water movement has increased the demand for accurate measurements of soil physical and hydraulic properties. Data on saturated hydraulic conductivity (K), which was measured by using different hydraulic heads, are presented for artificially packed soil columns and for different soil layers of undisturbed soil cores taken from a long-term experiment on conservation tillage. In the majority of the samples in both artificially packed soil columns and undisturbed soil cores, increasing hydraulic head caused significant deviation (i.e. significant positive correlation coefficient between hydraulic head and the measured values of K) from the conventional criterion for Darcy’s law that flux remains linear with hydraulic gradient. The study, therefore, emphasis the need to define the hydraulic head for measuring K values to be used for studying water movement in soils, to facilitate efficient utilisation of water resources for irrigating field crops in different soils and under different planting systems and irrigation methods.