Effects of By‐Product Sulfuric Acid on Phyto Availability of Nutrients in Irrigated Calcareous, Saline‐Sodic Soils

Abstract

AbstractSulfuric acid (H2SO4) is produced during the SO2 scrubbing process at Cu smelters, and “spent” H2SO4 is a waste product from oil refineries. A 2‐year field study was conducted on two irrigated soils high in salts and Na in southcentral Montana to evaluate the effectiveness of H2SO4 for improving nutrient availability and growth of barley (Hordeum vulgare). Treatments included several rates of smelter acid, and comparisons with gypsum (CaSO4·2H2O), spent acid, and feedlot cattle manure in combination with smelter acid. Levels of P, Fe, Zn, Cu, and Mn were measured in the soil, and plant uptake of these elements plus N, K, Ca, Mg, and Na were determined for the second‐year harvest. Sodium adsorption ratio (SAR) was measured in soil extract from the 0‐ to 5‐cm layer at harvest.Sulfuric acid was an effective amendment for improving soil nutrient availability, barley dry‐matter yield, nutrient uptake, and for reducing SAR and plant uptake of Na. Both smelter acid and spent acid were similar in their effects. Equivalent rates of gypsum and H2SO4 compared in this research were similar for increasing soil Zn, Cu, and Mn availability and for increasing nutrient uptake and barley yield. Sulfuric acid, but not gypsum, increased available soil P and Fe levels.Sulfuric acid used in combination with manure provided a substantial additional increase in available soil P, Zn, and Mn over acid used alone. The manure‐plus‐acid treatment raised available P in the surface 20 cm of soil from an initial level of 5 mg/kg to a level adequate for good crop growth (ca. 24 mg/kg). Manure plus H2SO4 produced the highest barley yield and nutrient uptake.