Effectiveness of By‐Product Sulfuric Acid for Reclaiming Calcareous, Saline‐Sodic Soils

Abstract

AbstractCopper smelters produce H2SO4 during the S scrubbing process, creating a continuing supply of H2SO4. Oil refineries use commercial grade H2SO4 in alkylation units and the resultant “spent” acid is a waste product available for other purposes. A 2‐year field experiment was conducted on two irrigated sites in south‐central Montana to evaluate the effectiveness of H2SO4 for reclaiming calcareous, salinesodic soils. Treatments included increasing rates of smelter acid, and comparisons with gypsum (CaSO4 · 2H2O), spent acid, and feedlot cattle manure in combination with smelter acid. Reclamation effectiveness was evaluated by analysis of saturated paste pH, electrical conductivity of the saturation extract (ECe), and sodium adsorption ratio (SAR) values of the soil in the 0‐ to 15‐ and 0‐ to 20‐cm depth intervals. Barley (Hordeum vulgare L) was grown both years as a biological test for reclamation.The degree of reclamation improved with increasing acid rate. Barley dry matter yield on plots that received the highest rate of acid was more than four times that of the check the second year.The effect of spent acid was similar to that of smelter acid. Gypsum lowered ECe and pH vlaues more than an equivalent rate of smelter acid, but SAR and barley dry matter yield were improved similarly by both amendments. Feedlot cattle manure plus smelter acid increased barley dry matter yield 40% over smelter acid alone. We propose that this effect is due to the improved soil nutrient status when both amendments are used together.