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 and commercial growers. Soil tests for home gardeners and commercial growers are conducted similarly, but when conducted for field crops, the report has recommendations that do not apply to home gardeners.
Always select a soil testing that provides recommendations for the home garden, lawn, or vegetable garden.
Any one of the soil testing labs listed can be selected. Compare costs, processing times, location, and/or available services to choose the best lab for you.
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 with recommendations specific to garden and lawn settings. This is not a complete list of laboratories, and no endorsement is implied. Please contact us if you wish to add a soil testing lab to this list.
- Waypoint Analytical
- Frontier Labs
- SoilWise – AgSource Soil Testing
- A&L Great Lakes Laboratories
- Midwest Laboratories
- Dairyland Laboratories
- SoilKit
How do I collect a sample?
All of the laboratories listed above provide detailed instructions on their websites on collecting and submitting a sample to their lab.
A soil sample is a mixture of many small samples collected from 10-15 locations across the area to be tested. Use a small trowel to collect the samples from the top 3 to 6 inches of soil, remove plant material and large roots, and mix them together. The soil testing laboratory's website, will provide more information on how large the sample should be and how to label and submit the sample.
In general, soil samples should represent areas managed similarly or areas where the same crops/plants are grown. If you wish to test soil in different settings, submit separate samples for separate tests. 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, conducting separate tests for specific areas is beneficial. 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 report 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. Occasionally tests can 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 electronically and sometimes as a hard copy. 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 the laboratories listed above will provide recommendations based on the garden setting (lawn, vegetable garden, etc.) or plants being grown in that area. Some give this as part of their analysis; others charge extra for the recommendations. As a homeowner, it is highly recommended that 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. Recommendations for appropriate fertilizer rates are 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:
- Garden Soil Management, Iowa State University
- Fertilizing in the Home Garden, Iowa State University
- Lawn Fertilization, Iowa State University
- Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants, University of Minnesota
How often should I conduct a soil test?
Home gardeners benefit from testing soil every 3 to 5 years or when problems with plant growth or health are observed.
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 must use specified testing procedures and prove consistent 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 once they become compliant again.
Approved soil testing labs can be found at this website: IDALS Commercial Feed and Fertilizer Bureau - Commercial Fertilizer
Click on “Certified Soil Testing Laboratories” found under "Soil Testing."
More Information
- Managing Garden Soil.
- Information about managing garden soil through tillage, integrating organic matter, soil testing, fertilizer applications, and more.
- Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants (PDF)
- Information from the University of Minnesota on interpreting soil test results and making management and application decisions.
- Iowa Soil Health Field Guide (PDF)
- Information about soil health and its importance to sustainable agriculture systems. Focused primarily on agronomic crops.
- Iowa Soil Health Management Manual (PDF)
- Information on soil function and evaluation and soil health management practices. Focused primarily on agronomic crops.
- Building Soil Health (PDF)
- A brief overview of soil health and management practices that improve soil health. Focused primarily on agronomic crops
- Soils - Iowa's Nature Series (PDF)
- Information about Iowa's rich soils; how they form, how scientists describe and classify them, and the conservation challenges they face.