METROP lawn fertilizer is a three-part fertilizer made with nitrogen, phosphorous, and potassium. Nitrogen helps to promote growth, phosphorous helps plants convert nutrients, and potassium helps maintain healthy leaf blades and roots. The proportions of each nutrient vary depending on the type of turfgrass and soil fertility. You can conduct a soil test to determine the right amount of fertilizer for your lawn. Soil test kits are available from your local county extension agent for a small fee.