by Connie Oswald Stofko
A couple of simple tests can tell you what steps you have to take to improve your soil– or let you know that you are already on the right track.
There are three kinds of tests you might do, said John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County.
The first is a pH test to find out how acidic or alkaline your soil is. Farfaglia recommends that every gardener do this test at least once.
The next step up is a nutrient analysis test. It can tell you the level of nutrients, such as phosphorus, potassium, calcium or magnesium, in your soil. The test may also look at the percentage of organic matter in the soil.
The third level of testing is for contaminants in the soil, such as lead or arsenic. Most gardeners don’t have to test their soil at this level, Farfaglia said. You might do this if you are concerned that there might have been lead paint on the outside of your house and you want to have an herb or vegetable garden there, or you might test if there was a history of a factory operating in the area. Read more about testing for soil contaminants here.
How to get your soil tested for pH or nutrients
Test for pH
Of all of the things to test for, pH is the most important, Farfaglia said.
Luckily, most of us probably have soil that falls into a good range for most plants, “But if the pH is off, it’s going to be hard to grow things,” he said.
You can find information on the proper way to take a soil sample for pH testing here.
To have your pH tested, you can go to a Cornell Cooperative Extension office and have it done. The fee for this test is about $2 or $3; it varies by county. Contact the Cornell Cooperative Extension office in your county for details. Sometimes Master Gardeners will hold testing clinics at various sites during spring and summer; watch our Events page for listings.
You can also buy a kit for testing the pH of soil at some garden centers such as Lockwood’s in Hamburg.
The test for pH probably doesn’t have to be done every year, but Farfaglia recommends that you do it at least once to provide a baseline.
Test for nutrients
The nutrients test isn’t done at Cooperative Extension offices; you mail a soil sample into a testing service.
There are private labs that do this or you can go through a testing service called Agro-One, which partners with Cornell. (The Cornell Nutrient Analysis Laboratory does some testing, but it directs you to go through Agro-One so that you can get not just test results, but recommendations on what to do to amend your soil.) You may be able to pick up a self-mailing box for Agro-One at your Cooperative Extension Office.
On the list of soil tests here, choose the one marked service code 833 for home and landscape, which costs $12. See the submission form here. On the form, you must indicate what group of plants you’re trying to grow (herbs, mixed vegetables, roses, etc.) so you can get the proper recommendations. Those plant groups are listed on the form.
This package of tests measures nutrients including phosphorus, potassium, calcium, magnesium, aluminum, iron, zinc and manganese. A test for pH is included in this package, so you don’t have to have that done separately.
This package also tests your soil sample for organic matter, which includes compost, leaves, grass clippings– anything that was once a plant, Farfaglia said. Organic matter is important in your soil for many reasons, which we discuss below.
What pH should your garden soil be?
The pH level that your soil should be depends on what you want to grow, he explained.
For most things, such as vegetables, flowers, deciduous trees and lawns, you’re aiming for a range around neutral. That would be a range from 6.5 to 7.2, or from slightly acidic to slightly alkaline.
Exceptions would be for plants that prefer acidic soil, with a pH around 5.5 to 6, such as blueberries, rhododendrons and evergreens. If your soil is alkaline, around 7.5, those acid-loving plants wouldn’t grow well, he explained.
Gardens with acidic soil tend to be south of Buffalo, around Orchard Park and Hamburg, or into Niagara County, Farfaglia said. In Niagara County you’ll find the acidic soil along the lake in the fruit-growing areas because the soil is sandy and light there. Gardeners who have heavy clay rarely have acidic soil.
What to do if your garden soil is too acidic or too alkaline
In general, if your soil is too acidic, you add lime, and if your soil is too alkaline, you add sulfur.
You can find these materials at garden centers. There are directions on the package to tell you how much to add, Farfaglia said. How much you use depends on the texture of your soil. If you have heavy clay soil, you would need to use more of the amendment material.
It takes awhile for the soil amendments to take effect.
“Lime especially takes months to react with the soil to cause a meaningful change,” Farfaglia said. “Fall is a wonderful to do this because it gives you several months for the soil to adjust.”
Depending on how far your soil is from your goal range, you may have to repeat this process with either lime or sulfur, but especially with sulfur.
“Sulfur often needs to be done for several years,” Farfaglia said. “If your pH is really high, it may take many years to get and keep the pH down.”
If you have just one bed or one container garden where you need to bring down the pH, you may want to add some peat moss. Peat moss has a pH of 4.0; it’s very acidic in nature, he explained. If you use peat moss, you won’t have to use as much sulfur and you may not have to keep using sulfur for as many years.
A note about peat moss: There are differing opinions on whether using peat moss is bad for the environment because it depletes peat bogs, or whether the supply of peat is larger than we think, Farfaglia said.
If you don’t want to use peat, Farfaglia said you could use pine needles or oak leaves, which are acidic, in your soil or in your compost.
Most compost is usually fairly neutral or slightly alkaline, he said, and using oak leaves will make a small difference in your compost, perhaps taking it from a pH of of 7 to 6.8. (Be sure to shred the oak leaves with your lawn mower before adding them to your compost, he added. Oak leaves don’t break down well naturally.)
Another option: choose different plants
Instead of struggling to change the pH of your soil, another option is to choose different plants that will grow in the kind of soil that you have. If your soil is alkaline, maybe you should choose to grow something other than blueberries.
“That can be more sustainable in the long run,” Farfaglia said.
Test for nutrients before you fertilize
Before you use fertilizer, you should test to see whether you even need to add any nutrients to your soil.
“In many cases, if you take care of your soil, you may not need fertilizer, or you may need just a little,” Farfaglia said.
You can test for nutrients, but don’t skip the pH test. If your pH is off, you could be throwing fertilizer on your soil without seeing any benefits, he said, because nutrients get bound to the soil particles when the pH is out of range.
Adding fertilizer to your soil when it’s not needed could cause you to have too much of a chemical in your soil, which can be just as bad as having too little. In addition, the elements in fertilizer, particularly phosphorous, can pollute our water.
If you have your soil tested with the nutrient analysis outlined here (service code 833), you’ll get recommendations on what fertilizer, if any, you need to add to the soil.
Why organic matter is so important to your soil
Organic matter is important for soil texture, especially with the heavy clay soil that is a problem for so many Western New York gardeners have, Farfaglia said.
Organic matter also helps introduce beneficial organisms into the soil, such as fungi and worms. It can provide nutrients so that you may not need to add fertilizer.
As we described above, compost can help keep your soil in a pH range that you’re aiming for.
“Adding organic matter is really key,” Farfaglia said.
Any soil that hasn’t been improved probably contains 2 percent organic matter, he said, but you want to aim for 4 to 5 percent organic matter or even higher.
If you have problems with your plants, “You have to start with the soil,” Farfaglia said. “Soil is very important.”