Salt removal in a saline soil using fall irrigation under subsurface grid drainage

Astudy was initiated during 1987 and 1988 to evaluate the effectiveness of grid drainage and fall irrigation in reclaiming an area affected by severe salinity due to canal seepage. Three test plots were established for the study: highly saline, standard pivot irrigation (plot 1); highly saline, standard pivot irrigation plus additional solid set fall irrigation (plot 2); and moder ately saline, standard pivot irrigation (plot 3). Subsurface grid drainage, with a mean drain depth of 1.4 m, was present at all three plots located along the main canal of the St. Mary River Irrigation District in southern Alberta, Canada. Water levels, drain outflow, electrical conductivity (ECe), and sodium adsorption ratio (SARe) of the saturation paste extract were determined. Under conventional center pivot irrigation, no significant reduction in ECeor SARewas achieved over the 14mo period. When additional fall irrigation (374 mm) was applied, with a solid set sprinkler system, a significant reduction in ECe of32% and SARe of27% was observed in the upper 0.15 m of soil. Similarly, ECe and SARe of the upper 0.30 m of soil decreasedby 18% and 13%, respectively. Significant resalinization of the upper0.30mof soil occurred over winter in all plots. Results demonstrated the ability of fall irrigation to leach salts from the top 0.30mduring a periodof lowconsumptive use, whichcould lead to reclamation. Long term monitoring would be required to determine whether a further and permanent decline in salinity could be achieved.