How to Test Your Soil (and Why You Should Do It)
When it comes to your plants, you can’t cheat. If you save, the results will be felt in your garden: plants that are stressed and susceptible to disease will produce less fruit and the fruit will be less tasty. To make sure they get everything they need, from nutrients to water, fertilizer, sunlight and warmth, you just have to do the work. And there is no more important contribution to crop production than soil. Every educated gardener will tell you to test your soil—and if you’re like me, you’ve avoided it because it seemed like a lot of effort and money. Let’s talk about the different ways to properly till the soil.
Home testing provides limited information and inaccurate results.
The market is full of little testing kits that look just like the pool testing kit you remember your parents used to test whether your pool needed chlorine. I’ve tried many of these kits and found the results to be spotty at best, but they’re good if you have a lot of places to test and are just starting the process. Based on the results, you’ll know whether your garden needs more nitrogen, phosphorus, or potassium, and in some cases, you’ll be able to know what your soil’s pH level is. This is important because some plants, like blueberries, have different needs than, say, tomatoes.
Home Soil Test Kits:
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Luster Leaf Soil Kit , 20 tests: $15.99.
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Luster Leaf 1605 Digital Soil Kit , 25 tests: $29.95.
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LaMotte NPK Soil Testing Kit : $48.99.
This form of testing requires a lot of prep work, so be prepared. Take a few disposable cups. They don’t have to be large—you don’t need more than eight ounces—but they should be clear. For each area of your garden, take a sample, place it in a cup, and then write on the cup where the sample came from. Add water to the samples, mix well, and then place the cups somewhere to let the dirt settle. At this point, each cup gives you enough water to test each element, so go one by one and record the results. Take these results to your nursery and they will help you decide which fertilizer is best and how much to use.
Professional Soil Testing Provides Clearer Results and Action Plans—At Additional Cost
The most any home kit will tell you is some basic information about the most common elements. What they won’t tell you is what micronutrients you need, and while this may not seem important, your tomatoes and peppers do depend on the available calcium in the soil. Plants also need iron, manganese, zinc, copper, boron and molybdenum, but home tests won’t tell you that. Professional tests will also tell you if there are heavy metals in the soil. At some point, you will want to have your soil professionally tested.
The best place to find a testing site is your local extension office. If you haven’t met yours yet, this is the perfect excuse. Your satellite office is key to finding local master gardeners and any resources available in your area. You can benefit from a wealth of local knowledge and tools. Find yours here. They will have information on where to test your soil, and the testing site will tell you what preparation they need, but generally you will scoop the soil (push the compost or other mulch to the side and pull it up to eight inches deep) from several different places, homogenize the sample and then sift it. A hori-hori is a good tool for getting a vertical slice of soil rather than just a scoop on top, but you can also buy a soil probe designed for just this purpose. Then simply follow the instructions to send the sample to the laboratory.
What to do with soil test results
Your local nursery or farm store can help you understand the results you are getting: they will be able to tell you exactly what amendments you need to correct your soil. However, to give you a general idea rather than a numerical score, you will see that the results are represented by the words “yes”, “no” and “maybe”. Yes, the amendments will increase profitability, no, the amendments will not increase profitability, and maybe the amendments can increase profitability. They will provide you with information on a long list of nutrients, including the elements mentioned above. Although these elements may seem to exist in a vacuum, they interact with each other to produce what your plant needs. For example, although calcium is incredibly important, tomatoes won’t be able to absorb calcium if they don’t have enough phosphorus.