Water Vapor Transport in Soils from a Pervaporative Irrigation System

Abstract

A novel method for irrigation with saline water uses a polymer membrane, formed into a tube, to treat and distribute the water simultaneously. The flux of water across the membrane occurs by the process of pervaporation, during which a phase change from liquid to vapor occurs. Thus, water arrives in the soil in the vapor phase. The experimental results presented in this paper demonstrate that, contrary to previous assumptions, soil vapor flows are a significant transport mechanism during pervaporative irrigation in dry soils. The soil water sorption properties affect the rate of condensation in the soil, which in turn affects both the water distribution in the soil and the loss of water vapor to the atmosphere. The flux from the tube becomes limited by high humidities adjacent to the external surface of the membrane. Thus, enhancing condensation in the soil or increasing diffusion through the soil increases flux from the system. These findings highlight the need to consider how plants might interact with water supplied in the vapor phase.