All the dusts were said to be about equal to each other as suppliers of calcium, and in comparisons with agricultural limestone (a single rock type) on yields of alfalfa, the cement kiln dusts “tended to be superior” to the limestone. Fortunately the researchers noted a few other elements in the rocks, concluding: “If applied at the rate of 4 tons the dusts would supply, on the average, 3 times the magnesium, 6 times the sulfur, 9 times the potassium (as soluble K) and, except for one dust that would supply only 9 times
