Heartland Water Initiative.pdf

Key factors contributing to phosphorus (P) loss from agricultural lands to surface waters include:

1. Source factors: Soil P levels, P application practices, and associated field management practices.
2. Transport factors: Erosion from rainfall, snowmelt, and irrigation events, surface runoff rate, and subsurface drainage.

Phosphorus Contamination of Surface Freshwaters

Phosphorus is often the limiting nutrient for aquatic vegetation growth, and excessive growth can lead to:

1. Eutrophication: Deterioration of water quality through overstimulation of aquatic vegetation, resulting in decreased oxygen, reduced light transmission, and production of algal toxins.
2. Water quality changes: Hurt fish populations, reduce water quality for recreation, and impart undesirable odors and tastes.

Regional Water Quality Issues

1. U.S. EPA Region 7: Includes Iowa, Kansas, Missouri, and Nebraska, where over 65% of rivers and streams and 80% of lakes and reservoirs are rated as impaired.
2. Ecoregions: Western Corn Belt Plains, Central Great Plains, Nebraska Sand Hills, Central Irregular Plains, and Ozark Highlands, each with unique characteristics affecting ecosystem quality and integrity.
3. Total P limits: Suggested ranges from 10 to 76 parts per billion (ppb) in streams and from 8 to 50 ppb in lakes and reservoirs, varying by ecoregion.

Forms of Phosphorus

1. Four common forms: Dissolved reactive phosphorus, dissolved unreactive phosphorus, particulate phosphorus, and total phosphorus.
2. Bioavailable P form: Conversion of particulate P to a bioavailable form is crucial for understanding freshwater quality.