Soil sampling for lawn or garden

Kari Lewis

With March here, we have more folks thinking of gardening and lawn work in the upcoming spring and now is the time to be potentially thinking of doing a soil test on that lawn or garden. Many homeowners do not soil test but use standard fertilizer rates which are given on fertilizer bags.  If this is your practice and your plants appear healthy, this is an appropriate fertilizer regimen to continue.  However, if your plants are not thriving or producing well or you suspect a potential nutrient deficiency or toxicity, soil sampling for the lawn or garden is recommended.  Gardens can have excessive nutrient levels due to high inputs of compost and/or fertilizer.  Excessive levels of fertilizer are not only a waste of money but can be harmful to your plants and the environment.

Now is a good time to collect a soil sample for the lawn or
garden if plants haven't been thriving or you suspect a
potential nutrient deficiency or toxicity.  

To obtain meaningful and accurate soil test results, it is important to correctly collect soil samples from multiple locations within your yard and garden. A minimum of ten samples should be collected and mixed from your garden, or from each 1,000 square feet (sq ft) of lawn to obtain a representative sample. Be sure to remove any mulch or lawn thatch before collecting your soil samples. If there is a visual or textural difference from one side of your garden or lawn to the other, submit separate samples.

Soil samples are best collected using hand probes or augers, available from your local Extension Office. An alternative tool to collect a 0 to 6-inch soil sample is a bulb planter (available at most gardening stores). Tools should be cleaned between each garden or area sampled and stored away from fertilizers to prevent contamination. Soil samples are generally a 6-inch-deep core from the soil surface.  Samples may be submitted moist or dry. They should be enclosed in a Ziploc bag, sealed, and labeled with your information.

You should schedule soil sampling to allow adequate time for soil analysis (~one to two weeks) and fertilizer application, if needed, prior to seeding or planting time. Also, soil tests are representative of current nutrient levels and do not necessarily reflect future conditions. Therefore, soils are ideally sampled yearly in the spring to best estimate growing season nutrient availability.

The MSU Extension publication, “Home Garden Soil Testing& Fertilizer Guidelines” available free online or from your local Extension Office, includes a list of labs where you can send your soil sample for analysis.  By communicating to the lab any concerns and what you plan to grow in the soil, for example squash, potatoes, and carrots, they can provide specific recommendations for your scenario in terms of nutrient needs.  Tests can range from $20 - $50 and typically take one to two weeks to receive results back. 

This material was taken from the MSU Extension MontGuide "Home Garden Soil Testing & Fertilizer Guidelines."