Transient Changes in the Soil‐water System from Irrigation with Saline Water: I. Theory

Abstract

AbstractTransient soil solution concentrations and salt precipitation rates in the root zone are shown to be influenced by the ion composition and concentration of the applied water and soil exchange complex as well as by the water uptake distribution and infiltration rate. Calculations are performed on three kinds of infiltration water to estimate the ionic composition of the soil solution, the rate of gypsum and CaCO3 precipitation, and the time to reach steady state for a given irrigation management. Solution concentrations adjusted for exchange interactions were shown to precipitate twice the quantity of salt in a given time, resulting in lowered solution concentration and altered composition of Ca2+, Mg2+, Na2+, and SO42‐ ion concentrations in the solution phase, with up to 1,600 days required to reach steady state through the top 150 cm for a leaching fraction of 0.05. The extent of precipitation is also found to depend strongly on the concentration of sulfate and degree of saturation with gypsum in the irrigation water. Diffusion and dispersion are also shown to influence the duration of the transient phase.