Part of the sulfur applied to well drained soils ends up in sulfate form. Sulfur is oxidized by soil bacteria and fungi. The plant absorbs the oxidized sulfate ion. Sulfate concentrations between 3 and 5 mg/L in the soil are adequate for plant growth. Sulfates are moderately mobile and may be adsorbed on clay minerals, particularly the kaolinitic type, and on hydrous oxides of aluminum and to a lesser extent iron. If the soils in the waste management system are irrigated, sulfates can leach into the subsoil and even into ground water. Under poor drainage conditions, sulfates are converted mainly to hydrogen sulfide and lost to the atmosphere. In some instances, they are converted to elemental sulfur in waterlogged soils.
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