{"id":1252,"date":"2019-06-25T09:20:04","date_gmt":"2019-06-25T16:20:04","guid":{"rendered":"https:\/\/blogs.cdfa.ca.gov\/FREP\/?p=1252"},"modified":"2026-04-02T13:05:46","modified_gmt":"2026-04-02T20:05:46","slug":"nitrate-quick-test","status":"publish","type":"post","link":"https:\/\/blogs.cdfa.ca.gov\/FREP\/index.php\/nitrate-quick-test\/","title":{"rendered":"Nitrate Quick Test"},"content":{"rendered":"\n

The\nnitrate quick test (NQT) is a cost-effective tool that can be used in nutrient\nmanagement planning to determine the residual soil nitrate concentration. The\nresults from the test can be used to improve fertilizer management and assist\ngrowers in accurately meeting crop needs. Here is an outline of the steps for\npreparing soil samples, conducting the test and calculating the results. <\/p>\n\n\n\n

Supplies<\/h2>\n\n\n\n
  1. Soil\nprobe or trowel<\/li>
  2. Buckets<\/li>
  3. Distilled\nwater<\/li>
  4. Calcium\nchloride (CaCl2<\/sub>)<\/li>
  5. 50\nmilliliter (ml) centrifuge tubes<\/li>
  6. Nitrate\nquick test strips<\/li><\/ol>\n\n\n\n

    Soil Sampling <\/h2>\n\n\n\n

    Soil samples for the NQT should be taken near planting or just before a sidedress fertilizer application is made. Sampling depth is dependent on the crop\u2019s active root zone. For vegetable crops, it is most often in the top 2 feet of the soil profile. Try to sample close to the root zone so that the sample is representative of what is available for the plants.<\/p>\n\n\n\n

    For each sample, remove the top 2 inches of soil, which is above the root zone.<\/p>\n\n\n\n

    Soil nitrate levels are often variable across a field. To account for nonuniform soil, move in a zig-zag pattern through the field and collect 8 to 10 samples.<\/p>\n\n\n\n

    Mix\nthe samples thoroughly in a bucket. Use this homogenized soil sample for the NQT.\n<\/p>\n\n\n\n

    For\nmore explanation about how to take soil samples, see \u201cSampling\nfor Soil Nitrate Determination<\/a>\u201d from the California Fertilization\nGuidelines (https:\/\/apps1.cdfa.ca.gov\/FertilizerResearch\/docs\/Soil_Sampling_Nitrate.pdf<\/a>)\n <\/p>\n\n\n\n

    Nitrate Quick Test<\/h2>\n\n\n\n
    1. Create solution.<\/strong> Add 5.6 grams (about 1.0 teaspoon) of calcium chloride to 1.0 gallon of distilled water.<\/li>
    2. Prepare test tube.<\/strong> Add 30 ml of the solution to a 50 ml test tube. <\/li>
    3. Add soil and shake.<\/strong> Add soil sample to the tube until the solution rises to 40 ml. Cap tube and shake vigorously.<\/li>
    4. Wait.<\/strong> Let the solution settle. Time will vary depending on the content of the soil, with clay soils settling slower.<\/li>
    5. Test.<\/strong> Dip test strip into clear solution for 1 second. Shake off excess water and wait 60 seconds. Compare to color chart.<\/li><\/ol>\n\n\n\n
      \"Illustrated<\/figure>\n\n\n\n

      Interpreting Results of the Soil Nitrate Quick Test<\/h2>\n\n\n\n

      How much nitrogen (N) is available to your crop? <\/h3>\n\n\n\n

      The nitrate test strip color chart\nmay be calibrated in different units, either parts per million (ppm) nitrate (NO3<\/sub>) or ppm nitrate-nitrogen (NO3<\/sub>-N).\nNote that milligrams per liter (mg\/l) is the same as parts per million (ppm),\n1:1. <\/p>\n\n\n\n

      If the color chart is calibrated\nin ppm NO3<\/sub>, results should be converted to ppm NO3<\/sub>-N in dry soil, by using a correction factor based on\nsoil texture and moisture. <\/p>\n\n\n\n

      Test strip reading (ppm NO3<\/sub>) \u00f7 correction\nfactor = ppm NO3<\/sub>-N in dry soil<\/strong><\/p>\n\n\n\n\n\n\n\t\n\t\n\t\t\n\t\t\n\t\t
      \n\tCorrection Factors<\/strong>\n<\/caption>\n
      \n\t\tSoil Texture<\/strong>\n\t<\/th>\n\t\n\t\tMoist Soil <\/strong>\n\t<\/th>\n\t\n\t\tDry Soil <\/strong>\n\t<\/th>\n<\/tr>\n<\/thead>\n
      Sand<\/td>\n\t\t2.3<\/td>\n\t\t2.6<\/td>\n\t<\/tr>\n\t
      Loam<\/td>\n\t\t2<\/td>\n\t\t2.4<\/td>\n\t<\/tr>\n\t
      Clay<\/td>\n\t\t1.7<\/td>\n\t\t2.2<\/td>\n\t<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n\n

      Example <\/h3>\n\n\n\n

      You have a test strip reading of 30 ppm NO3<\/sub>. The soil is a moist sandy loam (Average 2.3 and 2 to\nget 2.15). Your NO3<\/sub>-N in dry soil would be: <\/p>\n\n\n\n

      30 ppm NO3<\/sub> \u00f7 2.15 = 13.9 ppm NO3<\/sub>-N<\/strong><\/p>\n\n\n\n

      Meaning of the result <\/h2>\n\n\n\n

      Low levels (10 ppm or less)<\/h4>\n\n\n\n

      Soils\nwith less than 10 ppm NO3<\/sub>-N have a low supply of N. A fertilizer\napplication is usually justified, especially for fast-growing crops. However,\nlate in the season, low soil NO3<\/sub>-N values may indicate efficient\ncrop uptake or movement of nitrate below the sampled layer of soil. <\/p>\n\n\n\n

      Intermediate levels<\/h4>\n\n\n\n

      Intermediate\nconcentrations may indicate the need for a reduced fertilizer application rate.\n<\/p>\n\n\n\n

      Sufficient levels (20 ppm or more)<\/h4>\n\n\n\n

      Soils\nwith NO3<\/sub>-N levels above 20 ppm show that there may be enough\nnitrogen to meet imme\u00addiate crop needs, and additional N fertilizer application\nshould be postponed until retesting indicates that residual NO3<\/sub>-N\nhas declined. <\/p>\n\n\n\n

      The ppm NO3<\/sub>-N in dry\nsoil may then be converted to determine how many pounds of nitrogen are\navailable to your crop per acre by using a conversion factor. <\/p>\n\n\n\n

      If your soil samples were taken at 12 inches, multiply the\nnumber by 4. If you take soil samples to a depth of 6 inches instead of 12 inch\u00ades,\nmultiply your reading by 2.<\/p>\n\n\n\n

      Example <\/h3>\n\n\n\n

      Your\nstrip reads 13.9 ppm NO3<\/sub>-N\nand your samples were taken at a depth of 12 inches. <\/p>\n\n\n\n

      13.9 x 4 = 55.6 lbs nitrogen\/acre available to your crop <\/strong><\/p>\n\n\n\n

      Nitrate\nis mobile, especially in light-textured soils. Heavy rains and irrigation can\nreduce the amount of available nitrogen in the soil. By becoming familiar with\nthe NQT and interpreting your results, you can confidently make efficient changes\nto your fertilization plan. <\/p>\n\n\n\n

      References <\/h2>\n\n\n\n