Effect of Agricultural Sulfur on Characteristics of Different Calcareous Soils from Dry Regions of Iran. I. Disintegration Rate of Agricultural Sulfur and Its Effects on Chemical Properties of the Soils

Abstract

The use of elemental sulfur (S) is of special interest in Iran since most soils are calcareous and elemental S, as a byproduct of the petroleum industries, is readily available. Recently, the National Petrochemical Company (NPC) of Iran, has produced an agricultural sulfur (A.S.) that contains 90% pure sulfur and 10% bentonite. As the production of this compound is in the experimental stage, relatively little information is available on its disintegration and subsequent oxidation to sulfate in the salt-affected calcareous soils. The present study was initiated to improve the understanding of the disintegration rate of A.S. in soil, based on the determination of changes in some of the soil chemical properties. Six soil samples were collected from different sites of a dry region of Fars Province of southern Iran and A.S., produced by the NPC of Iran, was thoroughly mixed with 2 kg of soil at the equivalent rates of 0, 2, 4, and 6 t ha−1. The samples were incubated under room temperature and moisture content of field capacity for 8 weeks, and pH and EC values as well as sulfate, total nitrogen (N), phosphorus (P), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) concentrations were determined. The results showed that the disintegration rate was very low, and only 1.5, 2.3, and 2.0% of the applied A.S. levels (i.e., 2, 4, and 6 t ha−1) were oxidized to sulfate, respectively. The results of pH and EC values were well accorded with those of sulfate contents, and an increase in A.S. level, resulted in no significant changes in the nutritional constituents (except Mn) of the tested soils.