How to Test Nitrogen, Phosphorus & Soil Salinity

Call a local laboratory and arrange a time to submit your soil samples for analysis. When you speak with the laboratory, ask if they will provide you with the sample jars and a chain of custody form. If there is not a laboratory in your town, you can ship samples to the laboratory. The laboratory should tell you how to send the samples and tell you if there is a required time frame for the analysis.

Rake the surface debris from your garden before you collect the samples. You only need to clean the areas where you plan to sample so you do not collect excess plant waste or rocks in your soil samples.

Dig a 6-inch deep hole with a shovel to expose fresh soil. Use a clean, stainless steel spoon to scoop soil from the hole into a bowl. You can collect discrete soil samples or composite soil samples. A discrete soil sample is a single sample from one hole. A composite sample is a mixture of soil from multiple holes. For discrete samples, fill a sample jar from the bowl then clean the bowl before collecting additional samples. If you are collecting a composite sample, place soil from each hole into the bowl and mix the soil before you place it in the sample jar.

Fill out the chain of custody form and submit the samples with the form to the laboratory. The chain of custody form lists your contact information, the sample names and the tests that you want the laboratory to run on each sample. List nitrogen, phosphorus and salinity on the chain of custody form next to each sample name. Most laboratories will complete a soil analysis in two to four weeks and will provide you with a written report detailing the sample methods and results.

Read the laboratory report and determine if the nitrogen, phosphorous and salinity levels are appropriate for your garden. Because various plants require different environments, you should research the optimum environment for the plants in your garden. Retest your soil each year to maintain a healthy soil environment.