You didn’t think you would have to study for your soil test, did you? But the results can look like alphabet soup (with some numbers thrown in) if you haven’t done your research. We’ll teach you how to read a soil test report and what to do with the information.
Soil tests show you characteristics of your soil that you can’t see or feel but that are crucial for healthy grass and plant growth. Your soil analysis will tell you about the nutrients in your soil, the soil’s pH, the amount of organic matter it contains, and more — if you know what to look for.
- What’s included in a soil test report?
- Where to get a soil test
- How to take a soil sample
- How to improve your soil based on soil test results
- FAQ about soil tests
- When in doubt, test it out
What’s included in a soil test report?
The format of your soil test report will look different depending on where you get the test, but the content itself is mostly the same no matter where you go.
Here are the basic elements of a standard soil test and what they all mean.
Soil nutrient levels
The bulk of your soil test report will show the quantity of each plant nutrient in your soil. Some reports also may include a graph showing whether the recorded amount of each nutrient is low, optimum, or high.
What are these nutrients and why are they important? Plants need certain nutrients to grow strong and healthy, just like humans need our vitamins. Plant nutrients fall into one of three categories:
- Primary nutrients: Nitrogen (N), phosphorus (P), and potassium (K)
- Secondary nutrients: Magnesium (Mg), calcium (Ca), and sulfur (S)
- Micronutrients: Boron (B), zinc (Zn), iron (Fe), manganese (Mn), chlorine (Cl), copper (Cu), molybdenum (Mo), nickel (Ni), and cobalt (Co)
Plants need the largest amount of primary nutrients. They need significant amounts of secondary nutrients, but not as much as primary nutrients. Micronutrients are still important for plant health, but plants only need a small amount of them.
Your soil test might measure all or only some of the nutrients listed above. If you don’t see the full names of any of these nutrients on your report, look for their chemical symbols (the one- or two-letter abbreviation).
Different labs may report the quantity of each nutrient in parts per million (ppm) or pounds per acre (lbs/acre). The ideal measurement of each nutrient varies depending on your soil’s texture, CEC, base saturation, and the plants you’re trying to grow.
The average measurement of each nutrient for most soils is listed in the table below. These are the measurements you will likely see on your soil report. If your soil’s measurements are higher or lower, you may need to amend your soil to support healthy plant growth.
Healthy nutrient levels
|Average amount measured in ppm
|Average amount measured in lbs/acre
|N (may be listed as NO3, the nitrate most commonly found in soils)
|25 – 30
|50 – 60
|25 – 35
|50 – 70
|165 – 220
|330 – 440
|100 or higher
|200 or higher
|1,400 or higher
|2,800 or higher
|7 – 15
|14 – 30
|0.3 – 0.5
|0.6 – 1
|1 – 3
|2 – 6
|10 – 20
|20 – 40
|8 – 11
|16 – 22
|15 – 30
|30 – 60
|0.8 – 1
|1.6 – 2
|0.25 – 5
|0.5 – 10
|1 – 20
|2 – 40
|1 – 2
|2 – 4
It may seem strange that the average measurement of some secondary and micronutrients is higher than that of primary nutrients. But just because your soil contains a certain amount of a nutrient doesn’t mean your plants will get that much. How much of a nutrient your plants can absorb depends on base saturation, soil pH, and CEC (all of which we’ll discuss later). All the characteristics of your soil are related.
Note: Your soil test report also may include the element sodium (Na), but sodium is not a plant nutrient. The sodium measurement has to do with your soil’s salinity or salt content, which we’ll go over in a moment.
Soil pH, which measures soil acidity or alkalinity, only takes up one line of your soil report, but it’s just as important to plant health as plant nutrient levels. Your soil’s pH determines how well your soil can absorb each nutrient. Different nutrients are more or less available to your plants at different pH levels.
Soil pH is measured on a scale of 0 to 14. You can determine whether your soil is considered acidic, alkaline, or neutral based on the table below.
|Soil pH listed on your soil test results
|Your soil’s category
|0 – 6.5
|6.6 – 7.3
|Neutral soil (7 is true neutral)
|7.4 – 14
Most plants and grasses thrive in a neutral soil pH of around 6 or 7, but there are many plants that prefer acidic or alkaline soil. So, the ideal soil pH for your yard depends on what you want to grow.
Buffer pH: Your soil test report also may include a buffer pH measurement. There will only be a number in the buffer pH spot if your soil is too acidic. The buffer pH you see on your report is the result of your soil mixed with a lime solution (called a “buffer test”) in the lab. Use the buffer pH to determine how much lime you need to add to your soil to neutralize its low pH.
Cation exchange capacity (CEC)
Cation exchange capacity (CEC) is a somewhat complicated scientific concept, but what you need to know is that it measures your soil’s ability to store certain nutrients and release them for plant uptake.
The “cation” part of CEC refers to positively charged ions, which remain in the soil root zone thanks to their positive charge and don’t leach out of the soil easily.
Plant nutrients that are cations include:
Basically, CEC measures your soil’s ability to hang on to these nutrients. Your soil test report will show CEC measured in milliequivalents of charge per 100 grams of soil (meq/100 g) — but you don’t need to know what that means to understand what your soil test is telling you.
The important thing for you to remember is that the higher your CEC measurement is, the less likely your soil is to leach (lose) nutrients. Add organic matter or lime to your soil to increase its CEC.
The target CEC range for your soil depends on your soil type (sandy, clay, loam, etc.) and pH, so we can’t give you an exact number to look for.
See the table below for the average CEC of different soil types at a neutral pH of 7.0. If your soil pH is lower than 7.0, your CEC will likely be lower than the values presented here. If your soil pH is higher than 7.0, your CEC is probably higher, too.
|Typical CEC at soil pH of 7.0 (meq/100 g)
|1 – 5
|Sandy loam soils
|5 – 10
|5 – 15
|15 – 25
|Clay loam soils
|15 – 30
|More than 30
For more information about CEC and how soil testing labs measure it, see the University of Georgia Extension’s publication.
If your soil analysis includes base saturation (not all of them do), it will be listed under “base saturation,” “% saturation,” or a similar variant. Sometimes, reports will list the saturation of each measured nutrient separately, in which case you would see multiple measurements such as “K saturation,” “Mg saturation,” etc.
Now that you’ve located base saturation on your soil report, what does it mean? Base saturation is the percentage of the soil’s CEC taken up by base cations (as opposed to acid cations, which can be toxic to plant growth).
The base cations in soil include:
If your soil test includes base saturation, you’ll see a percentage listed for each of these four elements.
Just like with CEC, the soil’s base saturation increases with soil pH. Higher base saturation usually means more fertile soil because soils with a high base saturation contain fewer toxic acid cations and more of the essential plant nutrients potassium, magnesium, and calcium (recall that sodium isn’t a nutrient).
See the table below for the ideal saturation percentage of each base cation.
|Ideal base saturation in soil
|4% – 8%
|12% – 25%
|65% – 80%
|Less than 1%
Compare the base saturation on your soil test results to these values to find out if your soil contains too much or too little of these elements for optimum plant growth.
Organic matter (OM)
Organic matter is any material that comes from a living thing, including plants and animals. All soil is made of part organic matter and part rock particles.
Organic matter in the soil includes:
- Plant material such as decomposed leaves and grass clippings
- Microorganisms such as fungi and earthworms that help the decomposition process
The organic matter (OM) measurement on your soil test shows the percentage of your soil that this organic matter takes up. In general, the higher the OM percentage, the healthier the soil. OM in soil improves water infiltration, increases water holding capacity and CEC, and makes soil easier to cultivate.
For the very best soil, you want to see an ideal OM measurement of 4% to 6% on your soil report. If your number is lower than this range, add organic matter such as compost or aged manure to your soil.
Soluble salts (salinity)
Not all soil tests include a soluble salts measurement. But if yours does, it should be clearly labeled as “soluble salts.” The results will be reported in millimhos per centimeter (mmhos/cm), a unit that measures soil conductivity.
If your soil test includes a soluble salts measurement, the ideal result is 0.8 mmhos/cm or less. Soils with more soluble salts than that are considered saline, and only salt-tolerant plants can grow in them. Excess soluble salts can dehydrate your soil and cause drought stress in most grasses and plants.
On soil test reports that don’t include a soluble salts measurement, look at your sodium measurements to indicate excess salt problems. Too much sodium results in sodic soil, which usually has a high pH and causes plant rooting issues.
You may have sodic soil if:
- Sodium (Na) content is 160 ppm or higher
- Base saturation of sodium is higher than 1%
Whether your soil test shows high soluble salts or high sodium content, you can repair salt-affected soils with these methods:
- Improve drainage: Better drainage allows excess salts to leach out of the soil. Improve drainage by tilling or aerating the soil and adding organic material such as compost.
- Add gypsum: Gypsum reduces the soil’s exchangeable sodium content. The recommendation section of your soil test may tell you the rate at which to add gypsum to your soil if you need it.
- Leach the soil: Flush excess salts out of the root zone of your soil by leaching, which means adding a LOT of low-salt water to the soil. You may need to use as much as 27,152 gallons of water per acre (about 1.6 gallons per square foot), which is the amount of water needed to wet 1 acre of soil to a depth of 1 inch. Leaching can harm or kill your grass and plants, so only do this if the excess salts are already causing major plant problems.
Recommendations and notes
At the bottom of your soil report or on a second page, after the charts and graphs showing your results, you’ll see a section of text. This text is where the lab recommends how much fertilizer, lime, or other soil amendments you should add to your soil based on your results and the types of plants you listed on the test submission form.
The recommendations section may include another chart telling you how much of each material or nutrient to add. Most of the time, labs report these amounts in pounds per acre (lbs/acre).
You can still use the lab’s recommended application rates even if your yard is less than an acre. Follow the steps below to figure out how much of a certain material you need to purchase for your yard based on the lab’s lbs/acre recommendation.
- Step 1: Convert acres into square feet
1 acre = 43,560 square feet
So, if your fertilizer recommendation says you need 130 pounds of nitrogen per acre, that’s 130 pounds for every 43,560 square feet of soil.
- Step 2: Calculate the recommended application rate per square foot.
Application rate in lbs/acre ÷ 43,560 sq. ft. = Application rate in lbs/sq. ft.
In our example, that would be:
130 lbs/acre ÷ 43,560 square feet = about 0.003 lbs/sq. ft.
You would need to apply 0.003 pounds of nitrogen fertilizer per square foot of soil.
- Step 3: Multiply the application rate in pounds per square foot by your yard’s square footage.
Application rate in lbs/sq. ft. x square footage of your yard = Total amount of soil amendment needed
In our example, let’s say your yard is 10,871 square feet (the average U.S. yard size).
The calculation would look like this:
0.003 lbs/sq. ft. x 10,871 square feet = about 33 pounds
That means you would need to purchase 33 pounds of nitrogen fertilizer for your yard.
Keep in mind, different plants have different soil needs. You may not need to apply amendments to your entire yard.
For example, if you said on your soil test submission form that you want to grow blueberries, your soil test may recommend amendments specifically for growing blueberries. You only need to apply those amendments in the area where you’re going to plant blueberry bushes.
In addition to soil amendment recommendations, the lab may include other notes about your soil test in this section.
Where to get a soil test
You can get a soil test from your local cooperative extension. A cooperative extension is a program within a university that helps the community with issues related to gardening and agriculture. All 50 states have a cooperative extension from a state university.
Not sure where to find your county’s local extension office? You can look it up using this list of cooperative extensions nationwide.
First, you’ll pick up a soil test kit from your extension’s local office. Then, you’ll collect a soil sample and fill out the soil test submission form, which will ask for information like which grasses or plants you want to grow and which tests you want the lab to perform.
Once you’ve filled out your form and collected your soil sample, you’ll send them (along with payment) to your extension’s lab. They’ll send your results back to you, usually within one or two weeks.
How to take a soil sample
The accuracy of your soil test results depends entirely on the quality of the sample you send in, so you want to collect your sample correctly.
Here are some tips for taking a good soil sample:
- Represent the whole space: Collect 15 to 20 samples from all across your yard and mix them together to form one sample that represents the whole space, not just part of it.
- Be consistent: Take each of your 15 to 20 small samples from the same depth and in the same conditions. That means don’t sample soil from one section of the yard right after it rains and from another section of the yard on a dry day. You want to take a standard soil sample depth of 6 inches.
- Look for variations: If your yard has vastly different soil types, don’t mix them. You won’t get accurate results that way. Instead, separate the yard into sections based on soil type and test each section separately.
- Get an accurate sample: Don’t sample your soil soon after adding fertilizer, lime, or another soil amendment. If you do, the test won’t show your soil’s true fertility.
- Avoid contamination: Collect your soil samples in a clean plastic container. A metal container could affect the measurements of metals in your soil.
- Mix it up: Mix your smaller subsamples thoroughly by hand until they form one cohesive mound of soil. If the soil is too wet to mix, wait for a drier day to sample.
- Fill the bag: The size of your total representative soil sample depends on the size of the collection bag you get from your extension office. Whatever the size, your sample should fill the collection bag.
How to improve your soil based on soil test results
Does your test show numbers that miss the mark? You’re not doomed to a barren landscape. You can improve soil fertility with soil amendments. A soil amendment is a material, either organic or inorganic, that you add to your soil to make it more suitable for plant growth.
- Raise or lower soil pH
- Improve water and nutrient holding capacity
- Improve drainage
- Add specific plant nutrients
Use your soil analysis results to figure out where your soil is lacking and which amendments you should add.
FAQ about soil tests
Anyone can order a soil test from a cooperative extension service or a soil testing company (which you can find online). Soil tests are most common for commercial growers like farmers, but these resources are available for home gardeners and lawn care enthusiasts, too.
Normally, you should test your soil every three to five years.
If your last soil test revealed a problem and you added soil amendments to fix it, it’s a good idea to test your soil again after one year to make sure the treatment worked.
“Good” is subjective, but in general, good soil drains well, absorbs the right amount of plant nutrients, has a neutral pH, and contains plenty of organic matter.
A soil test will tell you if your soil has these characteristics, or you can look for these signs of good soil:
✓ Lots of earthworms
✓ Dark brown in color
✓ Feels cool and slightly damp but not soaking wet
✓ Easy to penetrate and dig up
✓ Grass and plants are growing thick and green
A soil test will tell you if your soil is unhealthy. But if you don’t want to go through the trouble of getting a soil test, you can look for these common signs of unhealthy soil:
✗ Dry, dusty, or cracked surface
✗ Difficult to penetrate with a shovel, spade, or other gardening tools
✗ Pooling water
✗ Grass or plant leaves are turning yellow, brown, or purple
When in doubt, test it out
A soil test might not be necessary for every home gardener. But if you continually have problems with your grass and plants and can’t figure out why, a soil test might help you find your solution.
Another helpful tip: Always get a soil test before starting a garden. You don’t want to invest time and care (not to mention money) into a garden only to find out you chose a spot with poor soil that doesn’t support healthy plant growth.
Once you’ve read your soil test, it’s time to get your grass looking greener. Call one of Lawn Love’s local pros to make your newly tested lawn shine.
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