Growth of winter wheat irrigated with diluted kraft pulp mill effluent on soils amended with gypsum and wood ash

Abstract

Supplementing irrigation water with effluents could reduce the need for potable water for irrigation and promote nutrient recycling, but may require additional amendments to deal with Na. In a growth chamber experiment, winter wheat was seeded into a control soil and to soil amended with either gypsum or wood ash applied at an equivalent rate of 15 dry t ha-1. Wheat was irrigated at a rate of 6 mm d-1 with distilled water (DW), kraft pulp mill effluent (KPME) and waste-activated sludge (WAS), and three KPME/WAS combinations. This included two KPME/WAS combinations diluted with DW to 25 and 50% (KPME/WAS:DW) to evaluate the effect on the nutrient uptake and biomass and the impact on soluble ions in the soil. Effluent applications increased wheat biomass up to 70%, and increases of 97 and 140% were observed in soils amended with gypsum and ash, respectively. Effluent applications increased soluble Na, Ca, and SO4, but only on the gypsum-amended soils, except those irrigated with WAS, had lower sodium adsorption ratio (SAR) than control soils by 0.7 to 3 units. Effluent combinations at the lower dilutions in combination with gypsum could be used to provide supplemental water with moderate increases in electrical conductivity (ECe) and SAR that would still be within tolerable limits of many crops.Key words: Effluent irrigation, electrical conductivity, gypsum, sodium adsorption ratio, wood ash