Phosphorus is a common nutrient found in lawn fertilizer and is one of the most problematic pollutants in stormwater. It wreaks havoc on aquatic ecosystems, particularly in streams and lakes. High levels of Phosphorus result in excess algae growth that depletes the water of oxygen, drastically reduces water quality and ultimately can cause fish kills.
It is important to decrease the amount of Phosphorus in order to improve watershed health and for most yards phosphorous is often unnecessary. A soil test will be able to determine whether a fertilizer with Phosphorus is needed.