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Soil Testing Resources for Home Gardeners
Soil tests for home lawn and garden settings in Iowa can be submitted to neighboring state universities and private laboratories. Soil tests are not available from Iowa State University.
Where can I submit a soil sample for testing?
Many soil testing laboratories provide soil tests specific to agronomic (field) crops. These labs generate recommendations for field crops that do not apply to the home garden, lawn, or vegetable garden.
The following university laboratories provide soil test results for home garden and lawn settings.
- University of Minnesota Soil Testing Laboratory
- University of Wisconsin Soil & Forage Analysis Lab
- Michigan State University Soil and Plant Nutrient Laboratory
The following private laboratories provide soil tests for home gardeners. This is not a complete list of laboratories and no endorsement is implied. If you wish to add a soil testing lab to this list, please contact us. The labs listed here provide soil test results with recommendations specific to garden and lawn settings. Soil tests for home gardeners and commercial growers are conducted in the same way, but these labs can provide recommendations for home gardeners.
- Waypoint Analytical
- Frontier Labs
- VAS Lawn & Garden Soil Testing
- A&L Great Lakes Laboratories
- Midwest Laboratories
- Dairyland Laboratories
How do I collect a sample?
All of the university and private laboratories listed above provide detailed instructions on their websites about how to collect and submit a sample to their lab.
In general, soil samples should represent areas that are managed similarly or areas where the same crops/plants are grown. A soil sample is a mixture of many small soil samples collected from 10-15 different locations across the area to be tested. You can use a small trowel to collect the small samples from the top 3 to 6 inches of soil, remove plant material and large roots from the sample, and mix them together. More detailed information on how to collect the sample can be found on the soil testing laboratory's website, including the technique for collecting the sample, how large the sample should be, and how to label and submit the sample.
Submit separate samples for separate tests if you wish to test soil in different settings. For example, conduct one soil test for your vegetable garden and a separate test for the lawn or perennial border. If areas are large or have different environmental conditions, it is beneficial to conduct separate tests for specific areas. For example, a shady and wet front lawn with heavy, clay-based soils should be tested separately from a sunny, well-drained lawn in the backyard.
When do I collect a sample?
For most gardeners, fall or early spring is the best time to conduct a soil test as it allows time for soil amendments to be added before the next growing season. However, a soil sample can be collected at any time when the soil is not frozen. Do not collect soil samples in extremely wet or dry soil conditions or just after applying lime, fertilizer, compost, or manure.
What is evaluated in a soil test?
Most basic soil tests tell you the levels of phosphorus, potassium, pH, and organic matter (%). Often they include or allow the option to add-on tests for lead, soluble salts, and other nutrients like calcium, magnesium, sulfur, boron, and micronutrients. Some laboratories will also provide the soil texture class (percentage of sand, silt, and clay) as part of the test or as an add-on. Nitrate levels can also be measured but the results require more interpretation because nitrogen's behavior in the soil is complex. Select laboratories can test for contaminants like heavy metals or herbicides, but these tests often require special processing and additional costs. Some labs also provide a soil microbial analysis telling you the biomass of bacteria, fungi, protozoa, and nematodes in the soil sample.
Once I submit a sample, what can I expect?
Most labs process samples in one to two weeks and provide an analysis and recommendations often as a hard copy, as well as electronically. Labs will provide recommendations based on the information you provide related to the type of plants growing in that area.
Once I receive the report for my soil test, what do I do?
All of the laboratories listed above will provide recommendations based on the garden setting (lawn, vegetable garden, etc.) or plants being grown in that area. Some provide this as part of their analysis, other labs charge extra for the recommendations. It is highly recommended that as a homeowner you select a test that provides recommendations for the lawn and garden.
The test results typically include information about soil fertility, pH level, and/or problems due to excessive salts or fertilizer materials. Recommendation for appropriate fertilizer rates is given to provide conditions for good plant growth without adverse effects on the environment. Click here to see a sample report from one of the labs. The laboratories listed above also provide resources on their website on how to read their reports and how to calculate the fertilizer requirements based on their reports. Utilize the report, accompanying recommendations, and the lab's online resources to apply fertilizers and soil amendments at the appropriate rate.
Additional information on soil and fertilization can be found in these publications from Iowa State University:
How often should I conduct a soil test?
Home gardeners benefit from testing soil every 3 to 5 years or when you observe problems with plant growth or health.
Where can I get a soil test done for larger, commercial operations (i.e. agronomic crops, acreages, row crops, small grains, hay, pasture, commercial horticulture, etc.)?
For these crops, clients should use soil testing labs that maintain certification through the Iowa Department of Agriculture and Land Stewardship (IDALS). For certification, labs have to use specified testing procedures and prove consistent test results. IDALS runs blind soil sample tests through these labs regularly. This list can change over time as labs may occasionally fail the blind tests but can return to the list with successful testing with IDALS next check.
To find this list of approved soil testing labs, visit this website; on the right side of the website click on “Certified Soil Testing Laboratories”.