Soil tests provide more helpful information on soils than any other resource. It is an inexpensive way to maintain good plant health in lawns and landscapes, and to maximize productivity of vegetable gardens and fruit crops. Soil test results pinpoint plant nutrient needs and soil test lab recommendations guide fertilizer applications so just the right amount is used. Test results also provide information for making plant selection decisions based on “the right plant in the right place” and a soil test can help diagnose what went wrong if good plants go bad. 

Soil samples are sent to a soil testing lab (see table at end of the fact sheet). Results will be sent back to you along with recommendations for taking corrective actions if needed. This includes the amount of fertilizers and other additives needed to support healthy plants. Reliable fertilizer recommendations can help horticulture professionals and gardening enthusiasts make decisions that support good plant health and save money!

A standard soil test will provide information on soil pH, cation exchange capacity (CEC), lime requirement index and base saturation. The soil test will also provide the status of phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg).

For additional fees, soil testing labs will provide information on iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) as well as a few other elements depending on the soil testing lab. Soil testing labs can also provide information on soluble salts, nitrates, soil texture and the organic matter content of the soil. The extra fees for these analyses may be justified if you are trying to solve a diagnostic problem by gaining information not provided through a standard soil test.

Why Do I Need to Soil Test?

The guidance provided by soil tests to horticulture professionals and gardening enthusiasts is sometimes compared to the guidance that blood tests provide to physicians. In this vein, a soil test is like a blood test for the soil. Soil tests can be used for four purposes: maintaining proper soil fertility; guiding plant selection; performing plant problem diagnostics; and for conforming to industry approved standard practices.

1. Maintaining Proper Soil Fertility. Healthy plants need certain levels of soil nutrients to thrive. Soil nutrients and fertility may fluctuate during the growing season. This is influenced by the quantity and availability of plant nutrients that are altered by the addition of fertilizers, manure, compost, mulch, and lime or sulfur, in addition to nutrient loss through leaching. Furthermore, large quantities of plant nutrients are removed from soils as a result of plant growth and development, and the harvesting of crops.

A soil test will determine the current fertility status and provide the necessary information to maintain optimum fertility year after year. Soil tests take the guesswork out of fertilization and are very cost effective; they eliminate wasteful spending on fertilizer products. Test results and recommendations help protect our environment by discouraging the overapplication of plant nutrients. Excess nutrients not used by plants may escape into groundwater, streams and lakes where they can contribute to environmental problems, such as algal blooms.

2. Guiding Plant Selection. Some plants will grow in a wide range of soil pH levels, while others require a narrow range of pH. Most turfgrasses, flowers, ornamental shrubs, vegetables and fruits grow best in slightly acid soils which represent a pH of 6.1 to 6.9. Plants such as rhododendron, azalea, pieris, mountain laurel and blueberries require a more acidic soil to grow well.

A soil test will determine whether the soil is acidic or alkaline. It is the most cost effective way to match the pH requirements of plants that you select with the pH of the soil in which you are planting.

	Figure 1: Colorado blue spruce showing a nutrient deficiency symptom. Photo by Joe Boggs, Ohio State University Extension.

3. Performing Plant Problem Diagnostics. Soil tests are an important tool for learning why plants lack vigor or are showing symptoms of other plant health issues. For example, Figures 1, 2 and 3 show a symptom, called chlorosis, that is typical of a nutrient deficiency in the foliage. If trees are exhibiting yellowing (chlorotic) leaves or needles during the growing season, a soil test may reveal whether the symptom is caused by a lack of an essential nutrient, a problem with the soil pH or both!

4. Conforming to Industry Approved Standard Practices. The American National Standards Institute (ANSI) is a private, non-profit organization that oversees the development process and approval of voluntary consensus standards for the private sector in the United States. The Tree Care Industry Association (TCIA) is accredited by ANSI to develop the actual standards known as ANSI A300 Tree Care Management standards. They are the generally accepted industry standards for tree care practices.

Following are recommendations from the ANSI standards specific to soil testing:

A300 (Part 2)-2011 Soil Management

• 14.4.4: Soil testing should be done prior to designing, plant selection, planting and/or developing management plans for landscapes.
• 15.2: Soil and/or foliar nutrient analysis should be used to determine the need, formulation and rate of fertilizer.
• 15.6.3: When new plants are specified, they should be tolerant of the native soil pH.

A300 (Part 6)-2012 Planting and Transplanting

• 63.3 Plant and site inspections for transplanting.
• 63.3.5 Soil at the installation site should be analyzed and tested for pH, structure, texture, density, nutrients and percolation.

Figure 2: Oak showing a nutrient deficiency symptom. Photo by Joe Boggs, Ohio State University Extension.	Figure 3: Red maple showing a nutrient deficiency symptom. Photo by Joe Boggs, Ohio State University Extension.

When Do I Soil Test?

A soil test is used as a planning tool and the first step in learning what you need to do, or not do. Soil samples can be taken any time of the year, as long as the soil is workable. However, you should allow plenty of time to receive and evaluate your soil test results, and then take action to improve your soil fertility. Any recommended adjustments, such as a fertilizer application, should be made at the appropriate time of the year. For example, fall is the best time of the year to make a lime application to raise the soil pH, while spring is the most appropriate time of the year for a sulfur application to lower the pH.

How Frequently Should I Soil Test?

A soil test every two to three years is usually adequate for maintaining soil fertility. Sample more frequently if you desire a closer monitoring of the fertility levels, or if you grow plants that require more nutrients. Soil tests for diagnostic purposes can be made as needed.

What Soil Sampling Tools Do I Need?

Figure 4: Soil probes provide a simple method for collecting soil samples Photo by Joe Boggs, Ohio State University Extension.

1. Soil Probe
   A soil probe is the easiest tool for taking soil samples. Soil probes quickly extract samples to a consistent depth simplifying the job of taking soil samples, especially when taking multiple composite samples. Soil probes are also useful for assessing soil moisture to monitor irrigation needs and for evaluating other physical properties of the soil such as compaction. Purchasing a soil probe is a good investment for horticulture professionals and serious gardeners.
   
   Figure 4 shows examples of some typical soil probes available for purchase. Others are also available. The T-handle step probe is recommended for more compacted soils or when collecting samples in a large area such as a lawn. The longer length and welded step reduces back and shoulder strain from bending over and applying pressure to insert the probe into the soil. Figure 5 shows how a soil probe is used to collect a soil sample beneath turfgrass.

2. Garden Spade, Knife or Hand Trowel
   A garden spade, heavy gauged knife (e.g., soil knife), or hand trowel as shown in Figure 6 can also be used to take thin slices or sections of soil for gathering soil samples. These tools require more time, effort and skill for taking precise soil samples compared to a soil probe. However, they are simple and effective if you are sampling loose soil, such as in vegetable gardens and flowerbeds. They are also cost effective for lawns and landscapes if you are only performing plant nutrient maintenance tests over small areas every few years.

Figure 5: Using a soil probe for soil sampling in turfgrass. Photo by Joe Boggs, Ohio State University Extension.	Figure 6: Using a hand trowel for soil sampling. Photo by Joe Boggs, Ohio State University Extension.

3. Plastic Bucket
   Soil samples should be collected in a clean plastic bucket or box as shown in Figure 7. Metal buckets, such as aluminum or zinc plated buckets, should never be used as the metals may contaminate the samples and influence the test results.

Figure 7: Soil samples should be collected in a clean plastic bucket. Photo by Joe Boggs, Ohio State University Extension.	Figure 8: This graphic shows five zones that will be soil tested. The stars in the graphic show where the subsamples should be taken. The subsamples should be taken in a zig-zag pattern, shown by the yellow-dotted lines. Graphic by Joe Boggs, Ohio State University Extension.

How Do I Take Soil Samples?

The validity of soil test results and recommendations depend on the quality of the samples taken and sent to a testing lab. Soil fertility varies throughout a lawn, landscape, fruit planting or vegetable garden. Because of this, the soil sample sent to the lab must be representative of the entire area. Submitting a composite sample reduces the influence of soil fertility variations. A composite sample is a number of individual subsamples randomly collected over the entire test area. The subsamples are mixed together and a small amount of soil, about 1 pint in volume, is sent as a representative sample to the testing lab. Figure 8 shows examples of subsample numbers and patterns to create a composite sample. The number of subsamples depends upon the size of the area being tested. In general, 5 to 10 subsamples are sufficient for small areas such as flowerbeds and 10 to 15 samples are recommended for larger areas such as lawns. Subsamples should be taken at random in a zigzag pattern over the entire area and each subsample should be taken to the same depth and soil volume. 

Soil Sampling Tips:

1. Separate soil tests should be used for:

• Areas that have received different applications for soil fertility programs.
• Soils distinguishable by color (i.e., light vs. dark), drainage or other factors.
• Different types of plant cultivation (i.e., turfgrass, vegetable gardens, trees/shrubs, etc.). Figure 8 shows different zones for soil sampling.

2. Sample when soils are suitable for spading or plowing.
3. Organic matter on top of the soil should not be included in soil test samples. Organic matter can affect the soil test results. This includes plants (e.g., turfgrass plants), the typical 1 inch or less “organic layer” typically found over Ohio soils, mulch, thatch, etc. Coarse organic matter, such as mulch or thatch, should be removed before taking a soil sample.

The organic layer included in soil probe (Figure 5) or hand trowel (Figure 6) samples should be removed prior to dropping the sample into a plastic bucket. Soil should be sampled to root depth, which typically means 5 to 8 inches for trees, shrubs, flowerbeds and vegetable gardens, and 3 to 4 inches for lawns. Of course, root depth may vary based on soil type and other conditions. Sample a vegetable garden between rows to avoid fertilizer bands where applications were made directly to plants.

How to Prepare Soil Samples for Submission

Figure 9: A typical soil test kit you will receive from the soil-testing lab.

1. Contact a soil-testing lab for instructions, soil test kits and appropriate forms. A list of testing labs is at the end of this fact sheet.
2. Break up lumps and air dry the soil on parchment or butcher paper (do not use newspaper or colored paper) at room temperature with no artificial heat.
3. Dry until the lumps can be crushed to the size of wheat grains or smaller.
4. Mix well and remove roots and other large pieces of organic debris as well as small stones or rock pieces.
5. Take about one pint of the composite sample and place it in the sample bag associated with the kit. 

Figures 9 through 13 below illustrate a typical soil test kit that you will obtain from the lab. Make sure the information on the forms is complete so you receive recommendations for your lawn, landscape, fruit or vegetable needs. Photos by Joe Boggs, Ohio State University Extension.

Figure 10: Complete all forms required by the testing lab.	Figure 11: Take about one pint of the composite sample to be sent for testing.

Figure 12: The bag is filled and ready to be sent to the testing lab.	Figure 13: The form is completed and ready to be mailed with the filled bag.

Where Do I Send My Soil Sample?

Table 1 at the end of the fact sheet shows a list of soil testing labs in Ohio and neighboring states as well as the types of materials they will test. The labs listed belong to the North American Proficiency Testing (NAPT) program that is operated under the supervision of the Soil Science Society of America (SSSA). For a fee, these labs will provide basic soil testing. Some labs also offer more advanced testing such as an analysis of soilless media, compost, plant tissue, and water as well as tests for soluble salts and the amount of organic matter found in the soil.

Contact the soil-testing lab before collecting the soil samples. Generally, soil-testing labs will provide a complete set of instructions, either with sample kits or upon request. Follow the instructions carefully. You will need to mail soil sample(s), completed sample form(s), and appropriate payment to the soil-testing lab selected.

How Long Does the Soil Test Take?

Soil test results and fertilizer recommendations are usually mailed in two weeks, depending on the testing lab. Make sure you read and follow the directions for filling out the soil testing form(s) accurately and completely; incomplete forms may cause delays in receiving results and recommendations. For example, unless you fill out the form for the types of plants you grow or will be growing, no recommendations will be given.

What Kinds of Soil Tests Are Available?

The kinds of available tests vary with different soil and tissue testing labs. Some of the common soil tests are lawn and garden, horticultural, agronomic, and soilless media test. Refer to Table 1 for a suggested partial list of soil and tissue testing labs and the types of tests available in Ohio and neighboring states. Please note the types of tests that individual labs offer may change without notice. Contact the lab for current tests available. The inclusion of a lab on this list does not necessarily imply any endorsement by The Ohio State University, nor does the exclusion of a lab imply any condemnation. Hence, The Ohio State University does not assume any liabilities associated with the selection and use of these labs.

References

• ANSI A300 (Part 2)-2011 for Tree Care Operations – Tree, Shrub, and Other Woody Plant Management – Standard Practices (Soil Management a. Modification, b. Fertilization, and c. Drainage). Tree Care Industry Association, Inc., Londonderry, NH. http://tcia.org/business/ansi-a300-standards/part-2
• ANSI A300 (Part 6)-2012 for Tree Care Operations – Tree, Shrub, and Other Woody Plant Management – Standard Practices (Planting and Transplanting). Tree Care Industry Association, Inc., Londonderry, NH. http://tcia.org/business/ansi-a300-standards/part-6
• Horneck, D.A., Sullivan D.M, Owen J.S., J.M. Hart. 2011. Soil Test Interpretation Guide. EC 1478. Corvallis, OR: Oregon State University Extension Service.
• Magdoff, F. and H. van Es. 2010. Building Soils for Better Crops, Sustainable Soil Management (3rd Ed.). Handbook Series Book 10, Sustainable Agriculture Research and Education (SARE), University of Maryland, College Park, MD. www.sare.org/Learning-Center/Books/Building-Soils-for-Better-Crops-3rd-Edition
• Weil, R.R., R.C. Weil, R.R. Weil, N.C. Brady, and R. Weil. 2016. The Nature and Properties of Soil (15th Ed.). Pearson Education, New York, NY.