A soil nitrate test will indicate the level of nitrogen in your soil. This is an important test for farmers or gardeners because it helps to tell you how much nitrogen fertilizer should be added to your soil to improve its structure. You will still need to test separately the levels of potassium and phosphorous in your soil.
Collect soil samples from up to 10 locations throughout your garden. Use a soil auger to remove 1 qt. of soil from each location. Put the soil into a bucket and mix thoroughly. Then collect 1 cup of soil into a clean glass jar.
Fill the jar to a point just above the soil line with clean distilled water.
Fold filter paper in half. Fold the paper in half again.
Open the filter into a funnel shape and push it into the jar quickly so that the cone touches the bottom of the jar. Plunging the funnel into the soil and water sample quickly will prevent the filter from absorbing water and tearing during the process.
Fill a water dropper with water that seeps into the cone.
Place 1 to 2 drops of this filtered water onto the pads on a nitrate test solution. One pad will measure the amount of nitrite in the soil sample. The other pad will measure the amount of nitrite and nitrate combined.
Compare the color of the test strip pad to the key on the side of the test strip container after 60 seconds to find the total amount of nitrite and the nitrite-plus-nitrate total.
Calculate the estimated amount of nitrate in your soil by multiplying this total by the measurement in centimeters of how deep you sampled your soil with the soil augur. Multiply this total by the bulk density of the soil. Multiply the total of all this by .089. Divide all this by 10.