Amelioration of a Sodic Soil through Thiobacilli Inoculation and Pyrite Application

Cultures of Thiobacillus thiooxidans Waksman and Joffe and T. ferrooxidans Temple and Colmer were enriched from an acid mine water. In vitro studies showed that inoculation of pyrite with T. ferrooxidans increased acid soluble iron and sulfate formation several fold T. thiooxidans enhanced acid and sulphate formation but reduced the soluble iron. Inoculation with both the cultures proved inferior to that with iron oxidisers alone. In column studies with highly sodic soil, surface application of pyrite followed by leaching was more effective in improving the soil than mixing. Inoculation with T. ferrooxidans after surface application of pyrite further enhanced soil improvement while addition of azide inhibited it. The involvement and relevance of bacteria in the oxidation of pyrite and improvement of sodic soils are discussed.