Phosphorus

Phosphorus can come from yard waste, fertilizers, animal feedlots, and wastewater.

Phosphorus (P), like nitrogen (N, found in ammonia, nitrite, nitrate), is an important nutrient for plants and algae. Because phosphorus is in short supply in most fresh waters, even a modest increase in phosphorus can cause excessive growth of plants and algae that deplete dissolved oxygen (DO) as they decompose. Excessive growth can also reduce the transparency of the water. Much of the excess phosphorus available to plants in the environment comes from farm and lawn fertilizers, runoff containing soil-bound phosphate, yard waste, runoff from animal feedlots, storm water, and certain industrial wastewaters.

Phosphorus in the Red River
The limits for phosphorus in water set by the North Dakota Department of Health (NDDH) and the Minnesota Pollution Control Agency (MPCA) are designed to prevent the excessive growth of aquatic plants and algae. NDDH has established an interim guideline limit for phosphorus at 0.1 mg/L. MPCA does not have a specific numeric limit for phosphorus but addresses the issue as part of a comprehensive strategy for phosphorus control.

Graph of phosphorus (mg/L) for the Red River in the FM metro area for the period July 2001 to December 2003 in relation to the NDDH standard of 0.1 mg/L (red line) for surface waters intended to prevent excessive plant growth.

Trends
A graph illustrating phosphorus levels in the Red River in the Fargo-Moorhead (FM) area is shown below. These levels are above the 0.1-mg/L interim guideline limit (red line) set by NDDH to protect the river environment. You can help reduce the phosphorus level in the Red River by properly applying fertilizer to lawns and gardens and properly disposing of yard waste.