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Kansas Geological Survey, Public Information Circular (PIC) 14
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Protecting Ground Water from Nitrate Contamination

In general, the means to protect ground water from surface contamination include proper well construction with at least 20 feet of grout to prevent surface and near-surface flow of water to ground water; wellhead-protection programs around public and domestic water supplies; maintenance and correct closure of septic systems; proper plugging of abandoned wells; mixing chemicals away from wells, streams, and ponds; and correct disposal of excess fertilizer and other chemicals. Most of these measures are aimed at preventing contaminants at the surface from entering ground water directly via wells and boreholes. The importance of proper well construction and proper plugging of abandoned wells cannot be overstressed. All the Groundwater Management Districts, as well as the State Conservation Commission and the Kansas Farm Bureau, have programs to assist with well plugging.

Agricultural-management practices that may reduce the potential for nitrate contamination of ground water include: (1) soil testing to determine the volume of nitrogen available; (2) determination of yearly fertilizer-application rate by use of a nitrogen-budget calculation that gives credits for existing sources of nitrogen, including manure fertilizer, nitrogen fertilizer, legumes, stored soil nitrogen, and nitrate in irrigation water; (3) timing of fertilizer (and water) application to the needs of the plants, including split applications; (4) use of nitrification inhibitors such as N-Serve® when applying fertilizer to delay the formation of nitrate; (5) utilization of crop-rotation practices instead of continuous cropping; (6) use of cover crops to minimize over-winter nitrogen losses; and (7) integration of livestock and crop production (including crop rotation) to recycle nutrients and use nitrogen efficiently. More information on most of these practices is available from the Kansas State University Cooperative Extension Service (address listed at end of report).

A simple equation for calculating the amount of nitrogen in irrigation water can determine the nitrogen credit as described in (2) above:

Depth of water applied (inches) x nitrate-N concentration of water applied (mg/L) x 0.227 = lb nitrogen/acre.

For example, applying 18 inches of irrigation water with a nitrate-N concentration of 5 mg/L represents:

18 (inches of water) x 5 (mg/L) x 0.227 = 20 lbs nitrogen/acre.

That 20 lbs nitrogen/acre applied in the irrigation water represents 20 lb/acre of fertilizer nitrogen that do not have to be applied. Using such a nitrogen credit and applying less fertilizer saves money while helping to protect ground water.

Efforts to control feedlot waste include (1) riparian-zone control to prevent surface runoff of waste to streams and ponds, (2) correctly built storage lagoons for liquid waste, and (3) rehabilitation of abandoned and intermittently used feedlots by growing plants to utilize excess nitrogen in soil.

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Kansas Geological Survey, Public Outreach
1930 Constant Ave., Lawrence, KS 66047-3726
Phone: (785) 864-3965, Fax: (785) 864-5317
Web version July 1999