Manipulation of soil texture to remove salts from a drip-irrigated root zone

Drip irrigation is a useful method for the application of low-quality water because it does not wet the foliage and limits the spread of contaminants. Nevertheless, when using water containing high levels of dissolved salts, drip irrigation may be insufficient for leaching and can lead to soil salinization. A new conceptual model was tested experimentally and numerically to examine if manipulation of the distribution of soils with different textures could promote the removal of salts from the root zone and increase leaching efficiency. The manipulated root zone consisted of a volume of coarse soil, located under a drip irrigation emitter, surrounded by finer texture soil. We hypothesized that the differences in hydraulic properties between the two soils and the capillary barrier developed at their interface would generate a one-directional flow path of the salty water from the location of irrigation to the fine soil. This would enforce salt accumulation beyond the root zone. The concept was tested in a series of lysimeter and Hele–Shaw chamber experiments, together with a two-dimensional flow model created in HYDRUS-2D. Results showed preferential salt accumulation beyond the coarse segment of the manipulated soil, providing a volume of leached soil sufficient to support a healthy root system. Under conditions of homogenous soil texture, a notable buildup of salinity was observed in the central root zone, whereas under the manipulated texture conditions, such salt buildup was not observed.