In modifying soil pH, the addition of amendments, fertilizers, tillage practices, soil organic matter levels, and drainage should all be considered. A common amendment used to acidify alkaline soils is sulfur (S) (Slaton et al., 2001). Elemental sulfur (S0 ) is oxidized by microbes to produce sulfate (SO4 2- ) and H+, causing a lower pH. Ferrous sulfate (FeSO4 ) and aluminum sulfate (Al 2 (SO4 )3 ) can also be used to lower pH, not due to SO4 , but because of the addition of acidic cations (Fe2+, Al 3+) (see Q & A #1). Application rates for these amendments will vary depending upon product properties (particle size, oxidation.
