Neither colloidal nor rock phosphate, but the consistency of rich soil. Comes from the washing piles left behind when high-grade ore was extracted to produce superphosphate in the early 20th century. Concentrations of available phosphate test regularly over 6%. Lowest concentration of heavy metals of any phosphate source. Apply 300-500#/acre, any season.
|OGS, 5# $7 / 50# $22|