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Fall is almost here! On this week's Good Growing Podcast, Ken talks about something we should add to our to-do list for this fall: conducting a soil test.
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Chris Enroth: cenroth@illinois.edu
Ken Johnson: kjohnso@illinois.edu
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What is Good Growing?
Talking all things horticulture, ecology, and design.
Welcome to the Good Growing podcast. I am Ken Johnson, horticulture educator with University of Illinois Extension coming to you today from Jacksonville, Illinois with a Gardenbite. On this week's Gardenbite, we're going to take a little bit of time to talk about giving your soil a checkup this fall, also known as soil testing. So as we begin our garden cleanup this fall, we should consider adding a soil test to the list of things that we're going to do. Soil testing is a relatively quick and easy task that has many benefits for us.
Ken Johnson:By conducting a soil test, it's going to allow us to see what the pH of our soil is, as well as what the nutrient levels are like in our soils. Conducting a soil test can be good for both our wallets and the environment. So again, knowing what those nutrient levels, what those pH levels are like in our soils, will help us to amend those soils to optimize the growing conditions for our plants. And by knowing the nutrient levels in our soils, that may lead to us using fewer fertilizers, which will save money and is going to be better for the environment. Applying too many fertilizers to the soil can lead to fertilizers leaching or running off into bodies of water and polluting them.
Ken Johnson:When it comes to plant growth, most flowers, shrubs, trees, grasses, vegetables, what have you that we grow here in Illinois are going to grow best in soils that have a pH between six point one and six point nine, or slightly acidic. And it's no coincidence that most nutrients that are going be used by plants are most readily available for plant uptake in this range. Now there are some plants, like rhododendrons, azaleas, and blueberries, that are going to grow best in more acidic soils. So if you grow any of these plants, or you want to grow any of these plants, conducting a soil test can help you determine if you need to make any adjustments to your soil pH. Improper soil pH is going to be one of the most common, if not the most common, reason why these acid loving plants like rhododendrons, azaleas, and blueberries struggle in many of our landscapes here in Illinois.
Ken Johnson:So when it comes to timing of soil tests, soil tests can be conducted at any time of the year as long as the soil isn't frozen and it isn't too wet. So if the soil is too wet to work, it's probably going to be too wet to soil test. So just let it dry out a little bit. Fall is a particularly good time to test soils, because any deficiencies that may be present can be addressed early on, and any amendments that you are going be adding to the soil are going to have time to react with the soil by the time spring rolls around again or starting to plant again. This is particularly important if we're trying to adjust the pH of the soil.
Ken Johnson:Now one thing I should point out when it comes to soil testing is that we don't need to do this every year in our home landscapes. Typically, we recommend people soil test every three years. You can soil test more often if you wish, but every three years is going to be good enough. Now before you conduct a soil test, there are a few things that you should ask the soil testing lab that you're going to be using. First is, do they accept home or garden or horticultural samples?
Ken Johnson:There are some labs that specialize in row crops or agronomic crops, corn and soybeans, and they don't do tests for gardens and things like that. So whatever lab you pick, make sure that they are going to do home samples and that they offer an interpretation with their results. Second thing to ask is do they have any special procedures for you to follow when you are collecting and sending in samples? Do they want you to put in a certain type of container? How much of that soil do they want?
Ken Johnson:And so on. Final thing you should ask is how much is it going to cost? We all want to know what we're getting into when it comes to the cost. In a lot of cases, soil samples are going run $15 to $20 $25 but it's probably a good idea to check on that before you send your sample in. Now you may be thinking to yourself, that's all fine and dandy, but I don't know who to call to get a soil test.
Ken Johnson:Well, you are in luck. University of Illinois Extension has a section on our soils website where there is a link to different labs around Illinois and the Midwest that will conduct soil tests. And you can find this on the soil section of the Illinois Extension website. You can go to extension.illinois.edu/soil and then go to the soil testing section. So when it comes to conducting a soil test, we want to make sure we are getting a representative sample of that soil.
Ken Johnson:So we want to check our soil's characteristics for things like the color, the texture, and the drainage. If the soil you want to test is uniform, you can take a single sample from that area. If your soil has varying characteristics, some areas are a little more sandy, some areas don't drain as well, taking separate samples is going to be a good idea of those different soil types. There's a good chance you're going to have to treat those a little bit differently when it comes to fertilizing or any other amendments you're going to make to them. We also want to have separate samples for the different parts of our landscape.
Ken Johnson:So for example, you don't want to mix lawn soil with a vegetable garden soil because these are going to be managed differently. We're going to fertilize our lawns differently than we are going to fertilize our vegetable gardens or flower beds. Also, if you have a problem area where you have plants that are not doing very well compared to similar ones in other parts of the yard, that's also an area that may warrant its own sample. So you can send in a sample from the problem area and the healthy area, and then you can compare those results to see if that problem is potentially soil related. So once you've got your different areas figured out of where you're gonna sample, we can actually now go and take our samples.
Ken Johnson:The first thing we want to do is remove any turf, residue, or other plant debris from the surface of the soil. Those residues and plant parts, they can affect the results you get from that soil test. We want to get as much of that stuff out as possible so we just have that soil. Next, we want to dig a hole, a small hole in the ground. If you're testing in a vegetable garden or flower beds, want to dig that hole six to eight inches deep, four to six inches deep if you're sampling from the lawn.
Ken Johnson:Once you've dug out that hole, you want to take a thin slice of soil down the side of that hole and collect that soil. Make sure to remove any roots or other debris from the sample, and then we're going to place that in a bucket. And we want to take at least eight random samples from that area that we're going to be testing. And you can do this by walking in a zigzag pattern over the area and just randomly stopping and gathering a sample. So again, we're gonna take eight to 10 samples from that area.
Ken Johnson:We're gonna take each of those samples, put them in a bucket, combine them all together, break up any clumps so it's a nice uniform texture, and then from that we're gonna take one to two cups of that combined soil, and that's what we are going to send off to that lab. Again, you can contact that lab to see exactly how much they want from you for that test. Once you have that cup or two, or however much you need, you can place that combined sample in a plastic bag or a bag provided by the soil lab. Then you want to make sure that you label that sample with your name, the date, and where the sample was taken. And this is particularly important if you're going to be sending off multiple samples.
Ken Johnson:So you want to make sure if you're doing it in lawn, vegetable garden, flower bed, you have three separate samples, you want to make sure you indicate which one is which. Then after that, you can gather all that stuff up, send it off to the lab. Most labs are also going to have a form that they want you to fill out as well, so fill that out, send it in, or however they want you to do that. So, just to summarize real quickly, soil testing can be good for both our wallets and the environments, help us use fewer fertilizers, which can save us money, help reduce the amount of runoff we get in bodies of water, reducing some of that pollution. We want to make sure we are getting uniform soil samples, so make sure that soil is consistent, looks the same, feels the same.
Ken Johnson:We want take separate soil samples from different parts of the garden. We want to take multiple samples from those areas, combine them all together for those different areas, and then send them off to the lab. So this fall, take a little time to give your soil a check up and find out what those pH and nutrient levels are like. Hopefully, you'll have a little bit more successful garden next year. That's all I've got for you for this week's Garden Bites.
Ken Johnson:Thanks for listening and keep on growing.