Extension

What would the garden soil be saying if it could talk to gardeners across the state? It might be referring to what may be lacking in the soil beneath the surface. Fortunately, gardeners don’t have to guess what their soil needs. A simple soil test can provide some valuable answers.

Late fall and early winter are good times to test garden and landscape soil. Soil testing is an important tool for home gardeners who want to get a head start on the next growing season.

Good soil is one of the foundations of a successful garden. But knowing whether the soil has adequate nutrients, or too much of a particular nutrient, isn’t something that can be determined just by looking at it. Soil testing provides a full picture of the nutrients available to plants and can help gardeners determine what type and amount of fertilizer, if any, is needed.

It’s also a cost-effective way to manage fertilizer use. Applying fertilizer without knowing what the soil actually needs can be a waste of money and may contribute to nutrient runoff.

It’s a good idea to do a soil test every two to three years for established gardens. Ideally, new gardens should be tested yearly because building healthy, fertile soil takes time. Regular testing can help gardeners track changes and adjust along the way.

Soil sampling isn’t difficult, but collecting a good sample is important. The goal is to collect soil that accurately represents the entire area being tested.

When testing a garden bed, collect several samples from different spots throughout the bed rather than taking all the soil from one location. Samples can be collected using a soil probe, spade or hand trowel. Take each sample to a depth of about 6 inches, making sure to remove plant debris from the soil surface first.

Collect 15 to 20 samples from the area and place them in a clean bucket. Make sure the bucket hasn’t been used to hold fertilizer, pesticides, cleaners or other materials that could contaminate the soil.

Mix the samples thoroughly in the bucket, then place about a pint of the mixture into a soil sample bag for analysis.

Soil sample bags are available at all Oklahoma State University Extension county offices. Soil samples can be submitted to the county office, too. The samples are sent to the OSU Soil, Water and Forage Analytical Laboratory for analysis.

Routine analysis is $15 per sample. The standard test evaluates soil pH, nitrate nitrogen, phosphorus and potassium. The results also include fertilizer recommendations based on the type of vegetation growing in the area sampled.

When filling out the sample label, be sure to indicate whether the sample came from a lawn, garden or another type of planting area. This information helps ensure the fertilizer recommendations are appropriate for the site.

One other important detail: Don’t put the soil sample in a plastic bag. Place the soil directly into the sample bag provided for testing. Soil samples are dried in an oven as part of the testing process, and plastic bags can melt.

A little time spent testing the soil now can help gardeners make better decisions when spring arrives. Rather than guessing what the garden needs, let the soil test provide the answers.

For more information about collecting soil samples, see OSU Extension fact sheet L-249, Soil Testing, the Right First Step Toward Proper Care of Your Lawn and Garden.