How to Test for Nitrogen in Soil


Nitrogen is an important nutrient that your plants need to grow. Nitrogen stimulates leaf growth and health in plants. If your plants don't have enough nitrogen, they may turn yellow and develop less foliage growth. The levels of nitrogen are often determined with soil test kits that also have the ability to check phosphorus and potash levels in the soil. It is important to test your soil each spring before planting your garden so that you know whether your garden needs a nitrogen amendment.

Step 1

Use a spoon to dig a hole about 3 inches deep for ornamental plant gardens or 4 inches deep for vegetable gardens. Remove about 1 cup of soil at that depth.

Step 2

Sift through the sample to remove wood, stones or anything else that may be in your soil. Place the soil in a plastic bag, and seal it closed.

Step 3

Use your hands to press the outside of the bag. Knead the soil in the bag to thin it out.

Step 4

Repeat the preceding steps to take a sample from each corner of your garden. Put each sample in a separate bag. Write the location where you got the sample on the outside of the bag.

Step 5

Mix your first soil sample in 5 cups of water in a large jar. Cover the jar and shake it well. Set the jar aside for 30 minutes to let the soil settle. Place each of your other samples in a separate jar and shake each well. Label each jar so that you know which corner each sample came from in your garden.

Step 6

Use the eye dropper with your test kit to remove some of the soil solution from the first sample. Add the liquid to the section of your test kit labeled "N Test" for nitrogen test. Add the solution until the tester is filled to the designated fill mark.

Step 7

Pull open a nitrogen test capsule that came with your kit, and release the contents into the solution. Put the lid back on your tester, and shake it well. Make sure to discard the capsule in the trash once you've emptied the contents.

Step 8

Wait 10 minutes for the color of the solution to change. Compare the color to the chart to determine how much nitrogen is in that particular area of your garden.

Step 9

Clean your test kit under running water. Remove the pH chart in the tester to clean behind it. Put the pH chart back in place, and continue to test the other soil samples. Add a nitrogen-rich fertilizer to areas of your garden that need more nitrogen in the soil.

Things You'll Need

  • Spoon
  • Plastic bags
  • Large glass jars with lids
  • Labels
  • NPK soil test kit with eye dropper


  • Biocontrol Network: Rapitest Soil Test
  • Hume Seeds: Testing Your Soil
  • Park Seed: Soil Test Kit
  • Lusterleaf: NPK Test Instructions
Keywords: testing for nitrogen, pH testing, amending soil

About this Author

Based in Ann Arbor, Mich., Robin Coe has reported on a variety of subjects for more than 15 years. Coe has worked on environmental health and safety issues in communities across Ohio and Michigan. Coe holds a Bachelor of Science in journalism with a double-major in international politics from Bowling Green State University. She has also received training and experience as a nurse aide.