Gypsum slotting to ameliorate sodic soils of Pakistan

Reclamation of sodic soils requires soluble calcium for exchange of absorbed sodium and adequate flow of water through and beyond the root zone to remove soluble sodium salts. Therefore, reclamation requires a combination of chemical (gypsum application) and mechanical (ploughing) measures. Traditionally gypsum is either broadcast or applied with irrigation water to the field prior to ploughing. Ploughing loosens the soil to a depth of 20–30 cm. Therefore, reclamation is restricted to shallow depths only. The slotting technique may overcome this limitation. This paper presents the results of a field study on the use of the gypsum slotting technique for reclamation of sodic soils in the Indus Basin of Pakistan. The treatments evaluated were gypsum application by broadcast method, gypsum application by the slotting technique and control (no gypsum application). All treatments improved infiltration rates. Reduction in salinity and sodicity was greater in slotted plots, compared to other plots. In inter-slot areas, both ECe and SAR were lower than control. Wheat and cotton yields in gypsum slotted plots were higher than the other plots. Copyright © 2005 John Wiley & Sons, Ltd.