Extractable Sulfate - Sulfur

For information about the importance of sulfur in soil and plants click here.

Readily soluble and adsorbed sulfates are extracted with a monocalcium phosphate [Ca(H2PO4)2] solution containing 500 parts per million (ppm) of phosphorus. A 10 gram scoop of air-dried soil is treated with 25 milliliters of extracting solution and shaken for 30 minutes. The sulfate in the filtrate precipitates with Barium (added in the form of BaCl2) and the SO4 concentration is determined turbidimetrically on the Lachat QuickChem 8500 Flow Injection Analyzer. The results are reported as ppm of extractable Sulfate-S in the soil.