How to Properly Test Your Soil
Last fall, I decided that it was time to expand my gardening knowledge by taking a local gardening class at nearby Clemson University. Did you know that some of the bigger Universities have day courses for the public? I think that it is a super cool idea for the community!
It was lovely to meet fellow gardeners from the area and I was pleasantly surprised with the information that I learned. One of the things that I learned from this garden class was about how to properly test your soil. I’ve always focused on the pH levels of the soil, but I learned that there are actually TWO tests you should do to your soil for well-rounded results.
Of course, if you can afford it, I highly recommend that you get your soil tested in a lab. They give you very thorough results and I found it very helpful for truly understanding my soil. I got mine tested at Clemson University (here’s their website), however, most U.S. states should have their own local/regional soil-testing labs. If you simply “google it”, you should be able to find a soil-testing lab near you. The soil-testing labs will give you plenty of information about your soil, including your phosphorus levels, potassium levels, pH levels, etc.
If you don’t want to use a soil-testing lab, *OR* if you like to compare/contrast their results with your own (ahem, that’s me…), here are the two tests you should do to properly test your soil at home.
Test #1: The Water Test
One of the fascinating things I learned in my gardening class was about the basic properties of soil. A good soil is a properly aggregated mix of sand, silt, and clay. This sand/silt/clay is held together with various organic matter. [Note: Aggregation means: “a material or structure formed from a loosely compacted mass of fragments or particles.”] One of the reasons why over-tilling and over-digging your soil is not good for your garden is because the more disturbance you do to your soil, the more you are damaging the proper aggregation of your soil.
When soil is properly aggregated, it will hold water (and nutrients) correctly. Too much or little of sand/silt/clay will make your soil either hold too much water (drowning your plants) or not hold enough water (quickly drying out your plants). Have you ever seen a beautiful pile of healthy soil? When you grab a handful of that rich soil and gently squeeze, it kinda sticks together. It’s not a rock-hard clump (like clay), or loose grains (like sand). Instead, it’s a delightful in-between mixture of properly aggregated soil.
To test your soil aggregation, simply dig out a large clod of dirt from your garden. Pour some filtered water into a mason jar, and gently put your clod of dirt into the jar. Gently shake the jar and wait for about 20-30 minutes. If the dirt clod completely falls apart/disintegrates in the water, then your garden soil is poor and disturbed (ie: NOT properly aggregated).
Preparedness Mama’s website has a similar Mason Jar Soil Test, where she wants to know the percentages of sand, silt, and clay in the soil. This Mason Jar soil test purposely breaks apart the soil in order to see what amendments need so be made. So, if you do the simple clod of dirt test and your soil clod easily breaks apart, you can learn a bit more about what to do to help your soil by doing the Preparedness Mama’s Mason Jar Soil Test.
Test #2: The Soil Test
The soil test is when you figure out what number/range your soil is on the pH scale. The pH scale ranges from 0 to 14, with 7 meaning neutral. Numbers less than 7 mean that your soil is acidic, and numbers greater than 7 mean that your soil is alkaline. Each type of plant prefers a different pH level. For example, blueberries love an acidic soil around 4.5-5.0. On the other hand, most vegetables prefer only a slightly acidic soil. Zucchini, for example, prefers a soil pH around 6.0-6.5. It is very important to make sure your fruits/vegetables/flowers/etc. have the necessary pH level for that type of plant. It’s one of the reasons why you need to carefully plan your garden carefully (here’s my post about garden planning) and use proper crop rotation techniques to make sure that, for example, your blueberries and zucchini plants aren’t in the same area of soil.
There are many different soil pH testers you can buy. You can go cheap (like me), and buy something like this, which is basically just litmus paper, a colored pH scale, and a tiny container to put your soil sample. This cheap little pH test has done just fine for me. It’s not super exact, but it ended up giving me a similar pH range that my official soil lab test sent me, so I will keep using this type of test. Someday, I will probably buy a fancy pH soil probe like this one. It’s kinda expensive, but it has great reviews and it will probably be WAY more accurate than the litmus paper version. While researching for this post, I found another pH tester that is way cheaper and seems like less work than the litmus paper, so I might try it this coming season. There are lots of options for pH testers, and they range in prices and techniques. Feel free to tell me about your pH testing technique in the comment section below!
After you figure out your soil’s pH level, you can decide what amendments to do to your soil:
- If you need to raise your pH level (ie: less acidic), you should add garden lime (like this)to your soil. You should try to use dolomitic lime if you can, because this type of lime is made up of both calcium and magnesium, both of which are good for your garden soil. You can also use wood ash to raise your pH level. Wood ash contains potassium and calcium, and, while not AS effective as lime, it will eventually raise your pH levels.
- Sometimes you need a MORE acidic soil (for blueberries, etc.). To lower your pH level (ie: more acidic), you should add both aluminum sulfate and sulfur.
Changing the pH range of your soil is not something that happens overnight. Do NOT just dump large quantities of your garden soil amendment(s) to the ground and expect results. Instead, add a little bit to your soil at a time and do this over a long time. For my blueberries, I personally add my soil acidifiers every spring and fall (twice a year). It will take a few years for the pH level to get where I want it, but that’s better than overdoing it and possibly ruining the soil. When you buy your soil amendments, the packages should tell you how much to apply per square foot.
Both of these tests will give you a great idea about the health of your soil. You will have a better understanding of the aggregation of your soil and the acidic range of your soil. When I did the tests to my soil, I found that my soil is mainly clay (no surprise there, I live in South Carolina) and that it has a pH level around 5.5. One of the best ways to fix an imbalance in my soil’s sand/silt/clay ratio is to add some coarse sand to my soil. This will help the soil eventually become a more healthy aggregated mix. I added homemade organic compost to the soil as well so that there is some organic matter to help the soil connect. I will also be adding some garden lime to my soil this spring to help raise the pH level a bit (though my blueberry patch should thrive this year!).