Fertilizer - Nitrogen and Groundwater Pollution (5008)

Nitrate pollution in groundwater can be a human health issue. For instance, drinking water with over ten parts per million of nitrate-nitrogen can cause blue baby syndrome. This means infants under six months old suffer from reduced oxygen levels in their blood.

Nitrogen is present in soils in several forms. Bacteria convert these forms into nitrate form. Nitrate is soluble in water and not tightly held by soil particles. Therefore, it travels through the soil with percolating water and contaminates groundwater supplies.

On existing lawns, nitrogen rates should not exceed one pound of actual nitrogen per 1000 square feet per application. Lawns should be fertilized one to four times per year, depending on turf variety and your desired maintenance schedule. Leaving grass clippings on the lawn is equivalent to about one fertilizer application annually.

On vegetable and flower gardens, application rates should not exceed 2/10, that is point two (.2) pounds of actual nitrogen per one hundred square feet. Applying nitrogen at these suggested rates should not lead to groundwater pollution.

To reduce nitrogen loss on sandy soils, use timed-release or slowly available fertilizers. These include organic sources and various slow-release forms of urea nitrogen.

Pollution problems related to nitrogen arise from animal manure, septic tanks, and fertilizer spills. As we have discussed here, the use of nitrogen fertilizers also contributes, especially on sandy soils. Applying fertilizer according to the above parameters will help keep nitrogen from contributing to groundwater pollution. 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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