Modelling capillary rise and soil salinity for shallow saline water table under irrigated and non-irrigated conditions

Salinization of soil is a major problem in arid and semi-arid regions with saline shallow water table. This is influenced by climate, soil type, crop, irrigation water quality and management practice, depth to water table, and salinity of the water table. Modelling can be used for estimating capillary rise and salinity of soil profile with saline shallow water table. The objective of this study was to modify a transient state analytical model (TSAM) for estimating capillary rise and salinity of soil profile with different saline water table depths and salinities under irrigated and non-irrigated conditions in a micro-lysimeter. In the modified TSAM variable root depth, non-uniform water uptake pattern and a more complete water balance equation were included. Modified TSAM resulted in good agreement between measured and estimated cumulative and weekly capillary rise for wheat experiment. Furthermore, this modified model predicted the capillary rise and salinity of different soil layers for various water table depths (0.3-1.20 m) and salinity levels (0.5-13.0 dS m(-1)) under irrigated and non-irrigated conditions accurately. However, the prediction accuracy of capillary rise for a highly saline water table (13.0 dS m(-1)) and shallow water table depth (smaller than 0.6 m) was rather poor. This might has been occurred due to the effects of high soil salinity in the root zone on the roots water uptake reduction. Furthermore, the modified TSAM responded accurately to both irrigated and non-irrigated conditions. When the application of the numerical models to larger irrigation areas with varying soil types, depth to water table and agronomic practice may not be feasible, the modified TSAM may be suitable for estimating short-term mean rate of capillary rise, net long-term capillary rise and season soil salinities in different soil layers. (C) 2003 Elsevier Science B.V. All rights reserved.