They both sound like something out of a horror movie, don't they? Bonemeal and blood meal are amendments that add nutrients to soil, and they can be used together. Blood meal is dried and powdered animal blood; it increases soil nitrogen levels. Bonemeal is ground animal bones; it increases soil calcium and phosphorus levels. Bonemeal also includes small amounts of magnesium, iron, zinc, and other trace elements that plants require. Blood meal and bonemeal take time to break down and make their nutrients available to plants. The plus side is that they are quite safe to apply around plants with little danger of burning from overapplication. On the downside, if your plants need a quick boost of fertilizer, they will act too slowly.