Quick test for soil nitrate

We have developed a quick, easy, on-site test that can detect excessive levels of soil nitrates. Although this test does not replace analytical testing, it provides values that are rough estimates of nitrate levels, and should be a useful and rapid diagnostic tool.

Materials needed:

• Hach water test strips for nitrate/nitrite (Cat. # 27454-25, Hach Company, PO Box 389, Loveland, CO 80539. Phone: 800-227-4224. A bottle of 25 strips is $16.29 as of July, 2010.
• Small beaker or container
• Tablespoon
• Soil from problem area and from nearby area of healthy turf
• Notebook for recording data

Procedure:

1. Mix equal volumes of soil and tap water (for example, 1 tablespoon of each) in a small container and stir thoroughly. Allow the soil to settle for 1 minute
2. Dip the test strip into the soil suspension.
3. Allow the strip to develop for 1 minute
4. Lightly rinse the strip with water to remove soil
5. Compare the color on the tip of the strip to the nitrate nitrogen color chart on the test strip container. Write down the ppm value that you think is closest to the color you see on the strip. This value must be converted to obtain the nitrate concentration (in parts per million) of your soil, using the formula below:

   (Dipstick value X 1.5) + 2.9 = Soil nitrate concentration (ppm)

   For example, assume that the color on your dipstick indicates roughly 15 ppm nitrate, as it does in this photo. Remember -- the dipstick value needs to be converted to one that is accurate for soil nitrate! The soil nitrate concentration is therefore = (15 X 1.5) + 2.9 = 24.9.

6. If the final value is over 20 ppm as it is in the example above, nitrogen applications of all types should be halted until levels are well below 20 ppm. If possible, leach the area to help bring nitrogen levels down more rapidly.

Keep in mind that the dipstick test has several limitations, including:

• It does not test for ammonium levels -- only for nitrate levels. Therefore, even if you have high ammonium levels in your soils, you will get a low reading from the dipstick.
• The test is designed to detect an excess of nitrogen, but it will not detect nitrogen deficits. To determine whether your soils are lacking in nitrogen, the soils should be sent to an analytical laboratory.
• The values you get with this test are rough estimates, at best. For more accurate readings, soils should be sent to an analytical lab for testing.