Sulfur Transformation in a Saline Sodic Soil of the Lajas Valley

Abstract

Data are reported herein from a laboratory study to determine the rate of sulfur transformation on a saline sodic soil of the Lajas Valley, Puerto Rico. The soil was alkaline and high in clay, cation exchange capacity soluble salts, and exchangeable sodium. Treatment differentials included the use of sulfur at rates of 4,8, and 12 tons to the acre furrow slice. Changes in the sulfate levels and pH were measured at monthly intervals from 1 to 6 months after applying the sulfur. At the first month interval sulfate levels were in the vicinity of 10 percent for all treatments. Sharper differences were measured at the end of the second month and thereafter until the fourth month. Final measurements showed rate of transformation of approximately 40,32, and 29 for the 4-, 8- and 12-ton treatments, respectively. The pH decreased up to the fourth month, at which time it increased despite the sulfuric acid formed as shown by the sulfur transformed. This is perhaps casual. Sampling techniques could possibly account for this fact. The decrease in percent of sulfur transformed with increase in rate of sulfur applied can possibly be explained on the basis of the Law of Chemical Equilibrium, since the product formed, gypsum, was not removed to enhance the velocity of the reaction to the right side of the equation. The relatively high tolerance of sulfur transformation organisms to high levels of free salts and exchangeable sodium is an important fact.