Subsurface Drainage System Performance, Soil Salinization Risk, and Shallow Groundwater Dynamic Under Irrigation Practice in an Arid Land

In recent years, several arid lands have faced themajor challenge of increasing risk of soil salinity caused by improper irrigation and drainage practices. Evaluating the relationship between soil salinity, drainage, and irrigation is therefore essential for understanding how to sustain the use of salinized soils in these lands. In this study, subsurface drainage performance, soil salinization risk, and shallow groundwater dynamic were evaluated under irrigation practice in a Tunisian arid land during two successive cropping years (2012-2013 and 2013-2014). Special attention was paid to the effect of subsurface drainage system on soil desalinization. Based on the analysis of the collected data, the following results were found: (1) frequent irrigation was a major factor in the rapid rise of shallow groundwater above critical soil depths; (2) inferior irrigation scheduling (i.e. large irrigation interval of 16-42 days) was the main cause of high soil salinization (ECe) around crop roots (ECe > 4 dS m(-1)); (3) the installed subsurface drainage system in the studied area (i.e. perforated corrugated pipe at a soil depth of 1.5 m) resulted in a substantial soil desalinization rate from the first to the second studied year, the average decrease in ECe was 23.3%; (4) the drainage system was unable to drain more than 27% of the salt introduced by the irrigation water due to the clogging of the gravel filter by sand. These results may provide a reference for appropriate restoration in the studied area and in other arid farmlands with similar condition.