Sul-Po-Mag, NPK: 0-0-18, 50 pound bag sold by GreenSense Ships in box fitting plastic bag to lessen shipping cost. Contains potassium sulfate and magnesium sulfate, a natural mined mineral. Great for tomato, potato, tuber and root crops. Non burning, low in chloride salt, neutral pH. Often a better fertilizer choice than potassium chloride or epsom salt.