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Nitrates in Your Well Water? Effects on humans, crops, and animals

running water in sink

If you’re buying property with a well you’ve probably been advised to have the well water tested for nitrates (among other things). Why do you need to be concerned about nitrates? What effect will high nitrates in the water have on your family, irrigated fruits and vegetables, and livestock you plan to raise for personal use or sale into the local food system? Here’s a list of online resources to help you evaluate the risk.

  • The acute health hazard associated with drinking water with nitrate occurs when bacteria in the digestive system transform nitrate to nitrite. The nitrite reacts with iron in the hemoglobin of red blood cells to form methemoglobin, which lacks the oxygen-carrying ability of hemoglobin. This creates the condition known as methemoglobinemia (sometimes referred to as “blue baby syndrome”), in which blood lacks the ability to carry sufficient oxygen to the individual body cells. Infants under one year of age have the highest risk of developing methemoglobinemia, followed by older persons who have a gastrointestinal system disorder resulting in increased bacteria growth. (NebGuide: Drinking Water: Nitrate-Nitrogen)
  • Testing for nitrate should occur any time a pregnant woman, woman anticipating pregnancy or infant under 6 months old becomes a water user. (NebGuide: Drinking Water: Testing for Quality)
  • If testing reveals high nitrate levels in well water, you may want to switch to a public or municipal water source for your home or invest in a reverse osmosis water treatment system. Reverse osmosis is effective at reducing several ions and metals, including nitrate. (NebGuide: Drinking Water Treatment: Reverse Osmosis)
  • Water with greater than 10 mg/L (10 ppm) of nitrate-nitrogen should not be used for drinking, but can be used for washing and rinsing produce. (http://safety.cfans.umn.edu/files/2013/03/Water-Testing.pdf)
  • Fruits, grains, and dairy products contribute almost no nitrate to people’s diets. (http://psep.cce.cornell.edu/facts-slides-self/facts/nit-heef-grw85.aspx)
  • Nitrate-nitrogen commonly occurs in well water, and by knowing the amount present, it can be accounted for, thus potentially reducing fertilizer input costs. (http://water.unl.edu/wells/testing)

well water hydrant

  • Nitrogen in the irrigation water has much the same effect as soil-applied fertilizer nitrogen; an excess will cause problems, just as too much fertilizer would (over-stimulation of growth, delayed maturity or poor quality). Since nitrogen is present in many water supplies, it is recommended that the nitrogen content of all irrigation water be monitored and the nitrogen present included as an integral part of the planned fertilization program. Sensitive crops may be affected by nitrogen concentrations above 5 mg/L. For example, grapes are sensitive and may continue to grow late into the season at the expense of fruit production; yields are often reduced and grapes may be late in maturing and have lower sugar content. In many grain crops, excessive vegetative growth produces weak stalks that cannot support the grain weight, resulting in severe lodging and difficulties for machine harvesting. (http://www.fao.org/DOCReP/003/T0234e/T0234E06.htm)
drip irrigation for grapes

With high nitrate levels in irrigation water perennial fruit trees and vines may continue to grow vegetatively late in the season reducing fruit yields, delaying maturity, lowering sugar content, and making plants more susceptible to cold damage.

  • High nitrogen water can be used as a fertilizer early in the season. However, as the nitrogen needs of the crop diminish later in the growing season, the nitrogen applied to the crop must be substantially reduced. Blending or changing supplies during the later more critical growth stages should be helpful. Another option is to plant a less sensitive crop, such as corn, which can utilize the nitrogen from the irrigation water more effectively. For crops irrigated with water containing nitrogen, the rates of nitrogen fertilizer supplied to the crop can be reduced by an amount very nearly equal to that available from the water supply. (http://www.fao.org/DOCReP/003/T0234e/T0234E06.htm)
drip irrigation on pumpkins

Test irrigation water for nitrates and subtract the amount provided from your nitrogen fertilizer application.

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