Whether you're getting ready to reseed your lawn or find yourself wrestling with problem areas, taking soil samples can help you solve lawn issues. Soil testing will tell you the soil pH and let you know if your lawn is missing key nutrients that it needs to be lush and healthy.
Lab or DIY Soil Testing
Many colleges and universities run agricultural cooperative extensions that will test your soil for you. They typically charge a testing fee, but the price can fluctuate widely from one extension office to another. The going rate for a soil test is anywhere from $20 to $100.
If you prefer a more hands-on approach or want to cut costs, you can buy a soil test kit at your local hardware store for around $20 and test the lawn yourself. Self-testing will provide you with quicker results since you can conduct the test yourself rather than waiting for the lab. Either way, the process of obtaining the sample is the same. Some test kits come with a soil probe to make sample collecting easier, but a garden trowel will do the job just as well.
How to Take a Soil Sample
Step 1: Wait for the Right Time
Technically, you can perform soil testing any time that the soil is dry and the ground is warm enough to obtain a sample. It's generally best, however, to gather a soil sample early in the spring. This gives you adequate time to address and repair any soil deficiencies before the growing season starts in earnest.
Always wait six to eight weeks between fertilizing your lawn and procuring a soil sample from it. Testing recently fertilized soil will skew your test results by adding nutrients to the soil that may not be there naturally. You'll get much more accurate information if you don't sample within eight weeks of fertilizing.
Step 2: Choose Your Sample Sites
If the conditions in your lawn are fairly universal, pick 10 random areas to sample. The soil pH and nutrient levels are probably the same throughout your lawn. Your soil may be different in different areas, however. If it is, make sure you take samples from diverse sites.
Part of your lawn, for example, may lie next to a small creek. Another area may receive more shade than the rest of the lawn or may see more traffic. The soil in these areas may test differently than the rest of the lawn. Keep this in mind when taking samples and clearly label them. In this instance, gather as many samples as you need to test all of the different conditions in your lawn.
It's also a good idea to test the soil around the dripline of any trees on your property. Plants feed heavily along this line and could be pulling resources from the soil, stealing it away from your grass.
Step 3: Clean Your Tools
Whether you're using a trowel or a soil probe, wipe it down with a clean towel and a little denatured alcohol. This ensures that you don't accidentally contaminate your soil and skew the soil test results.
Step 4: Take the Sample
To take a sample, dig a hole 6 to 8 inches deep in your lawn. Use your trowel to slice off a vertical layer of dirt about 1/2 inch thick. You can take the dirt slice from either side of the hole. Once you've secured the dirt slice, remove the sides of it and save the middle 1 to 2 inches. This is your soil sample that you will send to the extension service. Remove any grass, thatch or roots from your sample so that you have nothing but soil left. Repeat this process to secure a sample from all 10 of your chosen test sites.
Step 5: Package Your Sample
The test lab or sample kit you're using will contain small vials or containers. Simply place the soil in these containers per the test kit directions and then send them or drop them off at the test lab you've chosen.
Usually, the lab testing your soil will instruct you to combine all the soil samples you took into a bucket or bowl and then send a single sample for analysis. If you want to know specifics about different areas of your lawn, however, you may need to send more than one sample and pay for more than one test. You should not mix soils of different colors or textures nor should you mix samples from vastly different elevations.
When you need a general overview of your lawn's overall health, combining multiple soil samples into one works well. If you think different parts of your lawn need different types of help, however, consider multiple soil tests. In this case, label each sample with a number and write down where you took the sample so you can keep track of your results.
Step 6: Interpret Your Results
If you've sent your sample to a lab for soil testing, they will mail your results in a few weeks. If you test the soil yourself with a home test kit, you'll have answers immediately. Often, the lab results or test kit will explain to you what your test results mean, but you could have to do a little interpreting on your own.
Ideally, the soil pH in your lawn should register between 6.0 and 7.5. If it's higher or lower, you may want to add some amendments to raise or lower your pH and get closer to this goal.
Soil nutrients are measured in parts per million (ppm). For lawn growth, you want a phosphorous level between 12 and 25 ppm and a potassium level of 50 to 75 ppm. Your test results will also hopefully show 700 to 1,300 ppm of calcium and 140 to 270 ppm of magnesium.
Step 7: Amend Your Soil
If necessary, you'll need to adjust your pH level or fertilization techniques as indicated by your soil testing results. To lower soil pH, apply aluminum sulfate for a healthy lawn. If you need to raise your pH to amend acidic soil, apply agricultural lime to your soil.
Ideally, you should till in any soil amendments needed to raise or lower pH. This is easy if you're preparing to seed a new lawn but impractical if your lawn is already established. In this case, you can apply amendments to the top of the soil and water them in. This method takes longer, however, and you may not see an improvement in your lawn immediately.
- Pennington: How to Take an Accurate Soil Sample
- The Toro Company: Getting a Soil Test
- Cornell Coopertive Extension: How To Take A Soil Sample
- Purdue Turfgrass Science Program: Soil Testing for Lawns
- Spectrum Analytic: Interpreting Lawn and Garden Soil Test Results
- Turf: Understanding a Soil Test Analysis Report
Home is where the heart is, and Michelle frequently pens articles about ways to keep yours looking great and feeling cozy. Whether you want help organizing your closet, picking a paint color or finishing drywall, Michelle has you covered. If she's not puttering in the house, you'll find her in the garden playing in the dirt. Her garden articles provide tips and insight that anyone can use to turn a brown thumb green. You'll find her work on Modern Mom, The Nest and eHow as well as sprinkled throughout your other online home decor and improvement favorites.