Reclamation of a saline-sodic soil by gypsum and Leptochloa fusca

Amelioration of sodic and saline-sodic soils by chemical amendments requires high capital input. Cultivation of salt tolerant grasses may mobilize the native lime (CaCO3) in these soils through root action to substitute the chemical approach. A saline-sodic soil (pH(s) = 9.1, EC(e) = 9.8 dS m(-1), SAR = 103, CaCO3 = 9.4%, CEC = 122 mmol(c) L(-1), texture = sandy clay loam) was experimented for reclamation. Concrete cylinders (60 cm long, 30 cm internal diameter) were used to prepare the soil columns. The bottom of each column was padded with a 5 cm layer of gravel and sand to facilitate leaching. In each lysimeter, soil was added in small increments to obtain a uniform soil column. The soil was packed to a height of 40 cm, making the soil depth in each column 35 cm. Four treatments, one cropped i.e. kallar grass (Leptochloa fusca) and three non-cropped (control, gypsum @ 50%, and 100% gypsum requirement) were leached with four leaching cycles (LC(1) to LC(4)) at different time intervals. Canal water (EC = 0.28 dS m(-1) SAR = 0.8) was used for leaching. Two leaching cycles, LC(2) and LC(3), were completed during the peak growth of kallar grass (summer) and the remaining two, LC(1) and LC(4), were completed during winter when its growth was very slow. After the completion of LC(4), soil samples were collected from the lysimeters at 0-15 and 15-30 cm depths. The treatment receiving gypsum at higher rate (100% GR) removed the greatest amount of Na+ from the soil columns and caused a substantial decrease in soil salinity (EC) and sodicity (SAR). Performance of the grass treatment in enhancing the leaching of Na+ was between the gypsum treatments. Kallar grass removed more Na+ during summer than during winter. Effectiveness of the treatments for soil reclamation was in the order: 100% GR > kallar grass > 50% GR > control.