Quick answer
Soil testing for lawns and gardens is a lab analysis of a mixed soil sample that reports pH, nutrient levels and often organic matter, so you can choose lime, fertilizer or amendments based on what the soil actually holds.
Extension labs agree that a test is only as good as the sample. Depth, number of spots and cleanliness vary by state, so follow the instructions from the lab you will use. A county Extension office can tell you which lab serves your area.
Quick facts
The key facts about Soil Testing for Lawns and Gardens, with sources:
Key takeaways
- A soil test replaces guesswork. It shows pH, nutrients and organic matter so you add only what the soil lacks.
- The sample matters most. Extension labs ask for about 8 to 15 spots, a clean tool and one mixed sample per area.
- Sampling depth differs by lab: 2 to 5 inches for lawns and 6 to 8 inches for gardens in the sources we read.
- A lab test beats a simple kit. Montana State found simpler kits can differ moderately or highly from lab results.
- Retest on a schedule. Lawns need it every few years, vegetable gardens more often.
What a soil test is, and what it can and cannot tell you
A soil test measures what is in a small, mixed sample of your soil and reports it against ranges for the plants you grow.
Nebraska Extension lists the usual items: residual nitrogen, phosphorus, potassium, organic matter, cation exchange capacity (CEC) and pH 4. CEC is a measure of how well soil holds nutrients 6.
It can tell you whether pH is in range, whether phosphorus and potassium are low, optimum or high, and whether organic matter is low. Nebraska says the lab returns amendment recommendations based on the plants you list 4.
It cannot tell you why a lawn is thin if the cause is shade, drainage, compaction, disease or mowing. It also does not replace a look at soil texture or compaction.
Delaware’s circular puts it plainly: a test is only as accurate as the sample it is made on, and about half a pound of soil is used to stand for thousands of pounds in a lawn or garden 1.
How to take a soil sample, step by step
Steps follow the University of Delaware, Clemson, University of Tennessee and Nebraska Extension guides. Where they differ, we show it in the table below.
- Pick the areas. Sample the lawn, vegetable garden and shrub beds separately, and any area that has been treated differently. Delaware says each sample should represent only one soil type or condition 1.
- Use clean tools. A trowel, spade or sampling tube and a clean plastic bucket. Delaware says never to use tools or containers that held fertilizer or lime, because a small residue can badly contaminate the sample 1.
- Clear the surface. Remove turf thatch, mulch and vegetation 14.
- Collect the spots. Take small portions from about 10 random places across the area 13. Delaware says to cut a vertical slice about 2 inches thick to the sampling depth when using a spade 1.
- Mix. Combine all the portions in the bucket into one composite sample.
- Dry if wet. Tennessee says to air-dry wet soil on a paper plate and not to heat it 3.
- Fill the bag or box. Send about 1 to 2 cups, using the lab’s bag, per Delaware, Clemson and Nebraska 124.
- Label it. Name each sample and keep a record of the area it represents, and list the plants you grow on the form 14.
Keep the sample clean, and call 811 for any deeper digging
Contamination from fertilizer or lime on your tools or hands can ruin a test 1. Sampling is shallow, but if you plan to dig or trench while you are out there, call 811 first so buried lines are marked.
How four extension labs ask you to sample
| Lab or office | Spots per sample | Depth | Amount to send | Other notes |
|---|---|---|---|---|
| University of Delaware | At least 10; 5 to 6 spots around a tree or shrub | Lawns 4 to 5 in.; gardens and ornamentals 6 to 8 in. | Fill the lab bag to the line | Sample lawns and ornamentals every 2 to 3 years; vegetable gardens every 1 to 2 years 1 |
| Clemson Extension | 8 to 10 | Surface to 6 in.; 2 to 4 in. for lawns | 2 cups of mixed soil | Mix in a plastic bucket; label each bag by landscape area 2 |
| University of Tennessee Soil Lab | About 10 random locations | 6 in. | About 1 cup | Air-dry wet soil; do not heat it; record the sample number 3 |
| Nebraska Extension, Lancaster County | 10 to 15 cores | About 5 to 6 in., with a shovel | 1 to 2 cups | Remove vegetation and thatch; sample turf, ornamentals and gardens separately 4 |
Example: planning the samples for one yard
The yard is invented to show the method. The rules for how many samples come from Delaware’s circular and the counts and depths from the labs in the table 124.
| Area (example) | Separate sample? | Why | Spots and depth if following Delaware |
|---|---|---|---|
| Front lawn | Yes | Delaware says to sample separately where past treatment differed 1 | At least 10 spots, 4 to 5 in. |
| Back lawn that was never limed | Yes, apart from the front | Different treatment history 1 | At least 10 spots, 4 to 5 in. |
| Vegetable garden | Yes | Different soil use and a shorter retest cycle 1 | At least 10 spots, 6 to 8 in. |
| Shrub border | Yes | Ornamentals are sampled separately 14 | 5 to 6 spots around the plants, 6 to 8 in. |
| Wet corner where plants struggle | Yes, as its own sample | Problem areas should be sampled separately 1 | At least 10 spots in that patch |
That is five bags. Use the lab’s own count and depth if they differ from the numbers above. If you only send one bag, you get one average for areas that may not match.
Where soil tests come up: labs, kits, bids and lawn programs
At a county Extension office or land-grant lab. Delaware says sample bags, forms and instructions are available at county Extension offices, and that buying a sample bag pays for routine analysis 1. Nebraska names regional commercial labs that also take samples 4.
As a home kit. Hardware stores sell kits that give a color or a low-medium-high word rating. See the lab-versus-kit section below.
In a lawn care program. Some contracts promise a soil test; others skip it and apply by calendar. See the lawn care contract guide and ask whether a lab report backs each product.
On a landscape bid. If a bid lists lime, sulfur or compost, ask what test result supports it. The landscaping estimates guide shows how to compare lines.
In pH advice. The lawn soil pH page explains pH for turf, and this page covers how to get the number.
What a test gives you, and what it does not
What it gives you
Limits of home kits and of these figures
Montana State Extension says a kit that required sorting, drying and grinding soil gave results very similar to a lab, while results from simpler kits differed moderately or even highly from laboratory results.
It says kits typically mix raw soil with water, while labs dry, sort, grind and sieve it 5. It adds that kits may not include the correct phosphorus test and often report a word rating rather than numbers 5.
Montana also says the Olsen P test is accurate for soils with pH greater than 6 and Bray or Mehlich tests for pH less than 7.3, and that there is no simple conversion between them 5. That is why a report from one lab cannot be read with another lab’s ranges.
The depths and counts above come from four labs in four states. They show a range, not a national rule. We found no source that proves one depth is best everywhere.
Delaware’s circular was printed in 2007. Its sampling method is basic and still matches the other three, but ask your lab if its form has changed 1.
What drives the price and the wait, and how long a result lasts
We do not publish prices. Fees depend on the lab and on what you order. Delaware says buying the lab’s bag covers routine analysis and special tests are paid for in advance 1.
Montana State says lab fees vary from low to higher amounts per sample, and that it is better to pay for accurate results than to fertilize on wrong ones 5. Nebraska says results usually return in about two weeks 4.
A result is a snapshot. Delaware says lawns and ornamental areas need sampling every 2 to 3 years once fertility is established, and vegetable gardens every 1 to 2 years 1.
If you have added lime or a lot of compost since, retest after the slow change has had time, rather than a few weeks later 6.
Use the cost hub to see what shapes a landscaping bid that includes soil work.
What happens after you send the sample
Montana State says labs dry, sort, grind and sieve the soil before testing 5. The report comes back with your sample name, the values and a rating for each, plus recommendations for the crop you named 46. Ask the lab how it delivers results.
Your next moves are: read the report, ask the lab or Extension to explain unclear lines, apply what is called for by the label, and keep a record. If you hire help, give the report to the company and ask them to base lime, sulfur or fertilizer on it.
List what you will grow
Nebraska says amendment recommendations are based on the plants you list 4. A lawn, a tomato bed and a rhododendron border each need different advice, so say which is which on the form.
Keeping the testing habit going
Upkeep tasks are listed here without fixed dates. When to sample depends on your climate and when the ground is workable.
- Pick a regular interval. Delaware says every 2 to 3 years for lawns and ornamentals and every 1 to 2 years for vegetable gardens 1.
- Sample the same way each time. Same spots, same depth, same lab if you can, so the numbers compare.
- Sample when the ground is workable. Nebraska says any time the soil is not frozen; fall is best for amending 4. Delaware says sample well ahead of planting if lime is likely needed 1.
- Wait after adding lime or fertilizer. Retest after the change has time to happen 6.
- Keep your reports together. A folder of past results shows trends.
Warning signs a result may be wrong
- The result does not fit what you see. If plants thrive on a “low” reading, check the sample.
- You used a bag that was not the lab’s. Delaware says not to use bags other than those from the lab 1.
- The tool or bucket held fertilizer or lime. Contamination can ruin the result 1.
- The soil was wet when mailed. Tennessee says wet soil raises shipping costs and can weaken containers 3.
- A kit gave only “low, medium, high.” Montana says these ratings often lack a liming or fertility recommendation 5.
If results still do not explain the problem, ask your county Extension office, a certified crop adviser or a lawn professional. See also the lawn chemical safety page before you apply anything.
Rules and standards that apply
No federal rule requires a home soil test. We found none for single-family yards.
State fertilizer laws vary. States may limit when or how much fertilizer you can apply, and some tie that to a test. We did not load a specific state law for this page, so check your state department of agriculture and local rules.
Lab methods differ. Montana says Olsen, Bray and Mehlich phosphorus tests are not directly convertible 5. There is no single national test method for home gardens in the sources we read.
Product labels. Any lime, fertilizer or pesticide label is the legal guide. See lawn fertilization for how a test fits a program.
Lab test vs. home kit
| Feature | Extension or commercial lab | Home kit |
|---|---|---|
| Sample prep | Dried, sorted, ground and sieved 5 | Raw soil mixed with water or reagent 5 |
| Report | Numeric values and recommendations tied to field trials 5 | Often a color match or a low-medium-high word rating 5 |
| Phosphorus method | Can be matched to your soil pH, such as Olsen above pH 6 5 | May not use the right method 5 |
| Accuracy | Reference standard | Differs from very similar (one carefully prepared kit) to moderately or highly different (simpler kits) 5 |
| Recommendations | Amendment advice for the plants you list 4 | May not recommend lime or fertilizer rates 5 |
| Best use | Decisions about lime, sulfur, fertilizer and amendments | A rough check only; confirm with a lab |
- If You need to decide on lime, sulfur or fertilizer
- Then Send a sample to a lab. Montana says it is better to pay for accurate results than fertilize on wrong ones 5
- If You want a quick, rough pH look
- Then A kit may show a trend, but confirm any lime or sulfur decision with a lab 5
- If You are unsure which lab to use
- Then Ask your county Extension office. Montana says agents can help choose a lab 5
Common soil-test myths
- Myth One sample from one spot is enough.
- Reality Delaware says a good sample represents the area, with at least 10 spots mixed together, and that thousands of pounds of soil are represented by about half a pound 1.
- Myth A cheap kit gives the same answer as a lab.
- Reality Montana State says simpler kits differed moderately or even highly from lab results 5.
- Myth Test once and you are done.
- Reality Delaware says lawns need sampling every 2 to 3 years and vegetable gardens every 1 to 2 years once fertility is established 1.
- Myth Add lime and retest next week.
- Reality North Carolina State says lime can take up to a year to change pH 6; Delaware says lime reacts slowly 1.
- Myth Always add what the report shows as low, and more of the rest.
- Reality North Carolina State says adding phosphorus or potassium at or above optimum only adds nutrients plants do not need 6.
The local variable: your lab’s method and your soil’s pH
The right lab and the right phosphorus test depend on where you live.
Montana State says the Olsen P test is accurate above pH 6 and Bray or Mehlich below 7.3, and that Montana’s fertilizer guidelines rest on Olsen values because most of its garden and farm soils are above pH 6 5.
North Carolina State’s 50 to 70 optimum index range for phosphorus and potassium is for its own report scale 6.
Your county Extension office knows which lab and which scale apply in your state.
When to test, and your next step
Test before you add lime, sulfur, wood ash or a heavy dose of fertilizer, before building a new bed, and when plants struggle for no clear reason. It is also worth testing before you hire a company to apply anything.
Your next step is to find your county Extension office or state lab, get its bag and form, and follow its sampling instructions. Then read the report, and use soil amendments to match what the report calls for to the right material.
If you would rather have help, read the guide to choosing a landscaping company and ask each bid which test result its soil work rests on.
Questions about Soil Testing for Lawns and Gardens
How do I take a soil sample?
Use a clean trowel, spade or sampling tube and a clean plastic bucket.
Take small portions from about 10 spots in one area, to the depth your lab asks for, and mix them into one sample. Clear mulch and thatch first.
Send about 1 to 2 cups in the lab’s bag, with a label and the plants you grow.
How deep should I dig for a soil sample?
It depends on the lab. Delaware says 4 to 5 inches for lawns and 6 to 8 inches for gardens and ornamentals.
Clemson says surface to 6 inches, and 2 to 4 inches for lawns. Tennessee says 6 inches, and Nebraska says about 5 to 6 inches. Follow the instructions from the lab you will use.
How many samples do I need?
One composite sample per area that has the same soil and the same treatment history. Delaware says to sample the lawn, garden and shrub planting separately, and to separate front and back lawns if they were treated differently. Each sample is made of about 8 to 15 spots mixed together, depending on the lab.
Are home soil test kits accurate?
Not always. Montana State Extension says a kit that needed sorting, drying and grinding gave results very similar to a lab, but simpler kits differed moderately or even highly. Kits also often report only low, medium or high. For lime, sulfur or fertilizer decisions, a lab report is the safer base.
What does a soil test report tell me?
Nebraska lists nitrogen, phosphorus, potassium, organic matter, CEC and pH as typical items. North Carolina State says reports show a pH graph and a lime recommendation, phosphorus and potassium indices, organic matter and CEC. Each result is rated against ranges for your crop, with advice on lime and fertilizer.
How often should I test my soil?
Delaware says lawns and ornamental areas need sampling every 2 to 3 years once adequate fertility is established, and vegetable gardens every 1 to 2 years. Retest sooner after major changes, but give slow amendments time. North Carolina State says lime can take up to a year to change pH.
When is the best time to test soil?
Nebraska says testing can be done any time the soil is not frozen, and that fall is the best time to amend. Delaware says to sample well ahead of planting where lime is likely, because lime reacts slowly.
What does a soil test cost and how long does it take?
It varies by lab and by what you order, so check with the lab. Delaware says buying its sample bag pays for routine analysis and special tests are paid in advance. Nebraska says results usually return in about two weeks. Montana State says lab fees range from low to higher per sample.
Can I use a soil test to decide on lime or fertilizer?
Yes, that is its main use. North Carolina State says to apply lime only if the report calls for it, and that a lime value of 0.0 means do not add lime. It also says adding phosphorus or potassium at or above optimum adds nutrients plants do not need. Always follow the product label.
Sources
- University of Delaware Cooperative Extension, Circular 19, How to Take a Soil Sample for Home Lawns and Gardens (2007; text extracted from the PDF with pdftotext), retrieved .
- Clemson Cooperative Extension, Home and Garden Information Center, How to take a soil sample, retrieved .
- University of Tennessee Soil, Plant and Pest Center, How to Sample a Lawn or Garden, retrieved .
- Nebraska Extension in Lancaster County, Soil Testing and Amending, retrieved .
- Montana State University Extension, Soil Test Kits vs. Laboratory Tests (press release), retrieved .
- NC State Extension, Rowan County, Interpreting Soil Tests, retrieved .
Expert review
Written by the HyreYard Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Sampling counts, depths and amounts come from Delaware’s 2007 circular (read as extracted PDF text) and the Clemson, Tennessee and Nebraska pages, and are shown side by side because they differ. Kit-versus-lab statements are Montana State Extension’s. Report interpretation is North Carolina State’s and uses that lab’s scale only.
Suggest a correction. We fix errors and say what changed.