Author: Jessica Davis, Colorado State University
Phosphorus (P) is an essential nutrient for plants and animals of all kinds, but too much P can contribute to environmental problems. Phosphorus runoff from manured and commercially fertilized fields is an important issue because P can run off of fields and enter creeks, ponds, rivers, and lakes and can lead to a process called eutrophication. When this happens, the P essentially fertilizes algae in these water bodies and causes algal blooms. Basically, this results in scummy and stinky water with reduced value for things like drinking water and recreation. The algae out-compete other aquatic plants, and when they die and bacteria decompose the plant material, the bacteria use up the dissolved oxygen in the water. Under the worst conditions, this can lead to fish kills.
Manured fields with high soil P levels are potential environmental concerns. However, with proper manure management and best management practices to reduce runoff and erosion, two primary pathways for P movement, P losses from manured fields can be minimized. In fact, manure, especially higher solids manures, are very effective at improving soil quality, thus reducing P losses. Manure management plans that apply manure at the right time and in the right way to maintain soil P levels near crop requirements may have less environmental risk than commercially fertilized fields.
