Principle

The amount or Nitrogen available in soil for plant growth.

Calibration

To prepare calibration standards, take 5 ml of distilled water. Depending on if you chose minimal or full calibration, prepare standards as below.

Full Calibration

Standard Drops
0 kg/ha 0
10 kg/ha 2
20 kg/ha 4
40 kg/ha 8
60 kg/ha 12

Minimal Calibration

Standard Drops
0 kg/ha 0
20 kg/ha 4
60 kg/ha 12

Take 5 ml of the 0 kg/ha Nitrate standard, and add the contents of Reagent A and Reagent B. Shake till dissolved.

  • Take the resulting coloured solution and fill it into the white cuvette provided.
  • Place the cuvette under the light box and turn it on.
  • Place the phone over the stand.
  • Go to Settings > Colorimetric Test > Calibrate and choose Available Nitrogen under Soil.
  • Select the calibration point, 0 mg/l in this case.
  • Click on Start Camera.
  • Position the cuvette so that the middle, most uniformly lit portion is within the circle.
  • Select Analyze.
  • You should have your first calibration point. Repeat similarly with the other calibration points.

Extraction

Prepare an extraction solution by dissolving 1 teaspoon of table salt to 1 liter of water. Distilled water or deionized water would be ideal, but if you do not have access to it, then use tap water, RO Filtered water, or bottled water. Avoid using water from stagnant water bodies or groundwater. For the salt, do not use low sodium salt, rock salt, pink salt, black salt, or any such variant - simple store bought table salt should suffice.

  • Take 5 ml of soil in the measuring spoon.
  • Fill 25 ml of extraction solution in the measuring tube, and add the 5 ml of soil.
  • Close the tube, shake well and leave to settle.
  • Filter out the top clear layer of extracted solution.

If you are doing Nitrogen, Potassium and Phosphorous tests for the same sample, you can use the same extracted solution for the three tests.

Test

This test uses the Nitrogen reagents.

  • Collect 5 ml of extracted solution, add the contents of Reagent A and Reagent B and place in the white cuvette.
  • Place the cuvette under the light box and turn it on.
  • Place the phone over the stand.
  • From the home screen choose Colorimetric Test > Soil > Nitrogen.
  • Choose No Dilution if this is the first test, you might have to dilute the sample and retry later if you get an error.
  • Click on Start Camera.
  • Position the cuvette so that the middle, most uniformly lit portion is within the circle.
  • Select Analyze.
  • After some time, the app will display a result.