“…Composition, characteristics, and effectiveness of the slag as a liming material, and its attendant influence upon plant growth and composition have been reported (6,70,(72)(73)(74)(75). But where charges of unwashed brown rock phosphate or "matrix" were used in an industrial operation of the electric furnace, the resultant slag proved virtually devoid of liming value and hence enormous quantities of calcium and large amounts of included phosphorus of potential fertilizer value are locked within gigantic piles of relatively inert slag.…”