TIMELY AND EFFICIENT LEACHING OF FINE-GRAINED, SALT-AFFECTED SOIL

Timely leaching of salt from fine-grained soils is complicated by low soil matrix permeability. Additionally, leaching water use efficiency is highly variable due to effects of preferential flow through macropores. This study presents a conceptual model for timely and efficient salt leaching of fine-grained soil containing preferential flow paths such as root holes, worm holes and fractures. Results from a field irrigation experiment, demonstrate that leaching efficiency is highly sensitive to the degree to which near-surface generated macropore flow bypasses the saline soil matrix. However, by controlling soil moisture conditions using irrigation, it is possible to enhance mixing of water infiltrated through macropores with saline water in the soil matrix. Subsequent drainage of the soil matrix into the macropore network results in high salinity drainage to depth and good leaching efficiency. Cycles of infiltration and drainage are the operable mechanism of salt leaching in these fine-grained macroporous soils. The dynamic nature of soil moisture during infiltration and drainage make this process well suited to automated irrigation control. Real-time soil water tension measurements can be used to evaluate when to trigger irrigation. Improved leaching efficiency conserves water, while the relatively rapid leaching that has been demonstrated reduces the time required for salt-affected soil remediation/reclamation.