Interactions of calcium sulfite with soils and plants

CaSO3 is a by-product formed by several of the processes used for scrubbing SO2 from flue gas produced by coal-burning power generators. Using CaSO3 to improve the calcium status of acid soils would be a beneficial alternative to disposal in landfills. CaSO3 has biocidal properties and is used as disinfectant and food and drink preservative. It is important to evaluate under what conditions application to soils would not harm plant growth. Laboratory experiments confirmed that two transformations of CaSO3 occurred in soil systems: (1) decomposition to produce SO2 gas, and (2) oxidation to calcium suflate. Conversion to SO2 occurred in solution and soil at low pH, and acid soils treated with CaSO3 were initially toxic to seedling root growth. The degree of toxicity was time-dependent, with reduction in toxicity occurring as CaSO3 oxidized to calcium sulfate. Soil reaction also influenced toxicity, and at soil pH levels above 6, little seeding toxicity was evident