Hi Yield Iron Sulfate is formulated to prevent and correct chlorosis, the yellowing of plant leaves caused by iron deficiency, while helping create an acidic soil condition. One 3.25 lb. bag covers up to 875 sq. ft. For trees, apply ½ lb. per inch of trunk around the drip line; for shrubs, use 1 lb. per 2 ft. of height. Caution: product can stain concrete and pavement.