Growing season water and salt migration between abandoned lands and adjacent croplands in arid and semi-arid irrigation areas in shallow water table environments

Abstract

In arid and semi-arid irrigation areas with shallow water tables and fragmented arrangement of croplands and abandoned lands, dry drainage could be an optional management practice mitigating soil salinization. A dry drainage system lets non-irrigated abandoned lands serve as evaporative salt sinks receiving water and salt fluxes from adjacent irrigated croplands. Therefore, this research takes a typical dry drainage unit in the Hetao Irrigation District—one abandoned land and its adjacent croplands—as an example to directly reveal the field scale water and salt migration between abandoned lands and adjacent croplands. It was found that during the growing season, the water input, i.e. field irrigation and precipitation, raised the water table of the croplands and drove water and salt migration from croplands to the abandoned lands. However, the evapotranspiration in the croplands was also larger than that in the abandoned lands. Thus, during the intervals of irrigation (the “phreatic evaporation periods”), in some circumstances, evapotranspiration could drive water and salt flux from the abandoned lands to the croplands, which would influence the groundwater salinity of the croplands. Therefore, it is recommended to plant halophytes on the abandoned lands to enhance its evapotranspiration and hinder the water and salt flux from the abandoned lands to the croplands during intervals of irrigation. This management practice could help form more effective dry drainage systems between abandoned lands and adjacent croplands, and help better control the root zone salinity of the croplands.