Frequently Asked Questions about Phosphorus
What is phosphorus?
Phosphorus is a naturally occurring nutrient and under natural conditions enters the water through the weathering of rocks and precipitation of dust. Phosphorus is a limiting nutrient in freshwater systems and watershed areas. It is similar to nitrogen in marine environments in that when there is too much or too little it can change how an ecosystem functions. Phosphorus is never truly lost or destroyed; it moves from one system to another.
When is phosphorus problematic?
Increases in phosphorus can lead to problematic changes in freshwater lakes such as increased algae and a subsequent loss of deepwater oxygen. When phosphorus increases in the lake, algae (small microscopic plants) grow and the lake appears green. With excessive algal growth, the lake surface becomes scummy. There is less oxygen in the water as the algae decay and the lake loses its recreational appeal and value as wildlife habitat.
What affects phosphorus levels?
Wetlands slow down water flow and the plants nearby can absorb some of the phosphorus moving through. When wetlands are lost, this ability to remove the phosphorus from the system is eliminated. Phosphorus can also be adsorbed by soils, infiltrate the ground and be adsorbed by soil before entering surface water.
Phosphorus is often increased in streams and lakes by livestock manure, fertilizer from lawns and gardens, pet and waterfowl waste, wastewater flow from faulty septic systems and impervious surfaces.
What can I do to help reduce phosphorus levels?
During the summer months we want to enjoy a clear lake with low algae populations. Reducing the phosphorus coming into the lake and limiting algae growth is the best, and perhaps only, way we have of maintaining water quality in our lakes. You can help!
- Limit your use of fertilizer, apply at the recommended rate, and don’t fertilize before a storm.
- Yard waste can contribute significant amounts of phosphorus to the lakes. Keep soil, leaves, and lawn clippings out of ditches, storm drains, and streams by bagging them, composting them, or leaving them right on the lawn as natural fertilizer.
- Mow higher. Keeping grass length to 2½ - 3 inches is healthier for your lawn.
- Pick up pet waste. Pet waste can contain harmful bacteria as well as phosphorus. Flush it in the toilet or place it in the garbage.
- Control soil erosion around your house. When left bare, soil is easily washed away with rain, carrying phosphorus with it. Covering exposed soil with vegetation or mulch can prevent soil erosion.