Fertilizer - Phosphorous and Water Pollution (5009)

Phosphate is a major pollution concern in our lakes and streams. This is because high levels of phosphate support overproduction of algae and waterweeds. Homeowners may unintentionally contribute to the pollution problem.

Lawn and garden fertilizers are sometimes implicated as the pollution source. However, research has demonstrated that, with proper application, fertilizer is not a significant source. When phosphate is applied to soils, it binds to the soil particles. It becomes highly resistant to leaching or washing through the soil profile. Soil-bound phosphate becomes a problem when the soil erodes into the surface water. Erosion occurs from construction sites and sparsely vegetated ground. Be sure to contour soil from construction sites and establish vegetative cover where none exists.

Problems arise when fertilizer is spilled onto hard surfaces or applied to frozen ground. This washes with rain or snowmelt into storm drains and lakes. To minimize problems, sweep fertilizer off driveways, streets and sidewalks.

Street gutters kept free of plant residues have 30 to 40 percent lower phosphate levels in their surface runoff. Therefore, don't blow grass clippings and leaves into the street. Also, mow in a direction that blows clippings back onto the lawn rather than into the street.

Under intense rainfall or excessive irrigation, water may not be able to soak into the soil fast enough. Some runoff may occur. Then, soluble forms of phosphorus may be carried in the runoff water even from healthy lawn areas. Under normal conditions the amount of runoff from a healthy, relatively dense lawn is very low.

In summary, homeowners can take an active part in preventing lake pollution. Keep fertilizers, leaves, and lawn clippings off streets, driveways and other hard surfaces. In addition, prevent erosion by covering all slopes with turf or other plant materials. Water the lawn with about 1/4-inch to 1/2-inch of water after a fertilizer application. This helps move the material into the soil and reduces the potential of being lost in runoff.

We all have a part in protecting our water, a valuable resource. For more information, contact your local Extension office.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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