ABSTRACT
Alkali soils are widespread in several countries of the world and present a serious problem of immense practical importance for crop production in view of their inhospitable characteristics for plant growth despite inherent potentialities. There were two schools of thought as to the process by which S is oxidized in the soil. One emphasized chemical (auto or nonbiological) oxidation; the other biological oxidation. The same microorganisms that bring about S oxidation play important roles in biological oxidation of pyrite as well. The ultimate products of the oxidation of S in pyrite are sulfuric acid and iron sulfate. Carbon dioxide acts further on calcium carbonate to produce calcium bicarbonate, which is also a source of soluble calcium as shown here: The end products of the reaction of sulfuric acid (both primary and secondary) with calcium carbonate are soluble calcium sulfate and calcium bicarbonate. It is, however, advisable to develop some suitable method for direct estimation of pyrite need of alkali soils.
