Reclamation of salt-affected soils in the Goulburn Valley of Victoria

Abstract

A heavy soil (Goulburn loam) in the Goulburn Valley that was badly salinized was quickly reclaimed after control of the watertable to between 60 and 90 cm with subsurface drains. Within 16 months of installing slotted PVC drains 1 .5 m deep and 8.6 m apart, the electrical conductivity of a saturation extract decreased from 16.9 to 1 -9 mS/cm and crop yields increased substantially (oats from 1833 to 321 0 kg/ha, millet from 638 to 31 89 kg/ha). In addition, a white clover-based perennial pasture was established, which in the first season yielded 6985 kg/ha clover compared with 613 kg/ha in the absence of drains. The effects on the reclamation process and crop productivity of ripping the soil to 40 cm, applying gypsum at 10 t/ha, or a combination of both treatments were investigated. No soil treatment was effective without drainage due to the persistence of the shallow saline watertable. With drainage, gypsum applications decreased exchangeable sodium from 8.3 to 3.7% and increased hydraulic conductivity from 1 12 to 24.4 cm/d in the surface 15 cm. Gypsum also increased infiltration by 40%, leaching of chloride by 33% and yield of oats and clover by 44 and 29% respectively. Ripping either alone or combined with gypsum was of no added benefit