Effect of Sulfurous and Sulfuric Acids on Soil Properties and Growth of Soybean

The annual production of sulfur is high in Iran because the country has large resources of fossil fuels and sulfur is a byproduct of oil refining. Most of the produced sulfur is used in the production of sulfuric acid. Sulfuric acid (H2SO4) has been successfully used for reclamation of calcareous soils. This experiment was conducted in 2011 in a completely randomized block design with three replications and three treatments to compare the efficiency of sulfurous acid with sulfuric acid in water and soil quality and plant growth. The treatments included control (without use of acidic water pH=7. 6)، and two acidic waters made by sulfuric acid and sulfurous acid (both with pH=6). To evaluate the effect of treatments on soil chemical properties، soil moisture of the pots was raised to field capacity moisture content and was air dried. After seven irrigations، certain soil properties such as pH، EC، OC، P، K، Mn، Fe، Zn، and Cu were determined. Then، soybeans were planted. During cultivation، irrigation (according to treatments) was performed by acidic waters. Some growth parameters such as leaf color، plant height، dry weight of stems and leaves، and leaves nutrients were measured. The data were analyzed with SAS software and charts were drawn by EXCEL. The results showed that pH of irrigation water was reduce from 7. 2 to 5. 5 by injecting SO2. The effect of treatments on soil organic carbon (OC) and soil pH were negligible. But، the amount of salinity، potassium، phosphorus and micronutrients had significant differences with the control treatment. The effect of treatments on soybean leaves showed that the concentration of nitrogen and potassium were not significantly different between the treatments. But the concentrations of the leaves micronutrients (Fe، Zn، and Mn) were significantly different from the control treatment. The effects of sulfurous acid with pH=6 were almost similar to that of the sulfuric acid with pH=6 in irrigation water. Use of acidic water increased Fe، Zn، P، and Mn in soy bean.