A review of sodic soils research in the Queensland sugar industry

Sugarcane production under rainfed conditions was shown to be reduced by 1.5 t/ha for each percentage increment in exchangeable sodium percentage (ESP). Elemental sodium was found to be non-toxic to the cane plant. Any adverse effects on crop production of sugarcane, in the absence of high salinity, was associated with deterioration of soil structure and the consequent effects on water entry, its redistribution in the soil and the resulting plant available water. These effects were demonstrated clearly during amelioration studies where depth and quantity of soil moisture and plant water movement were measured. Partial reclamation of irrigated sodic soils was achieved by reducing the natural slope from 0.49% to 0.07% while maintaining the integrity of the topsoil. Further reclamation of sodic soils was achieved by application of gypsum or lime. Gypsum was shown to be the most effective on alkaline sodic soils, while both gypsum and lime were similarly effective on acid sodic soils. Sugarcane yields on fully irrigated sodic soils with ESP less than 25 were improved by up to 25% with the application of gypsum at 10 t/ha or by applying 2 t/ha annually dissolved in irrigation water. Promising, but not significant, yield improvements were obtained by changing the irrigation method from the conventional furrow technique.