1. Field and Laboratory Studies of Acid Sulfate Soils

Drains are introduced into acid sulfate (AS) soils grown to sugar cane to prevent waterlogging and drain runoff water. Drains have the potential to promote deleterious reactions and facilitate the transport of the resulting reaction products into the ecosystem. A field experiment was carried out to investigate the hydrology of an AS soil field and monitor the quality of its drainage water. Results have shown that in such low-conductivity soils, a steep water-table draw-down occurs close to the drain. Farther away from the drain, water-table dynamics are predominantly driven by evapotranspiration. The concentration of sulfate ions in the drainage water showed a steep decline during infiltration followed by a moderate surge during drainage. A laboratory leaching column experiment has revealed an increasing sulfate concentration away from the drain. The column experiment confirmed earlier findings of Rassam and Cook, who conducted hypothetical numerical simulations and showed that solutes from low-conductivity AS soils are mainly leached from soils located close to the drain.