Every year, I find myself getting asked how to amend gardens and raised beds with soil amendments. This can be easy to do, but there are a few steps that should be taken before applying anything. The first thing that should be determined is what your soil type is. What is the percentage of sand, silt, clay, and humus? I like to perform what is called a mason jar soil test to get that information. This is an easy process that will involve mixing a soil sample into a jar and taking some measurements after the soil settles. Steps for doing this can easily found online.
Once you get the results, the next step is to get a soil test. This will tell you what the soil is lacking or has too much of. Most states, through their Departments of Agriculture, county agricultural extension services, or public universities, provide free or low-cost tests, but unless you have someone that can help translate the results, you may want to spend a little extra to get a more comprehensive test. We use Waypoint Analytical (previously A & L Analytical). Their test results are really easy to follow, giving you a chart that shows each element in low, fair, or adequate amounts. They will also show pH and organic matter percentages.
Once you get your test results, you can then begin to map out what type of amendments would be beneficial to your soil. We commonly look at nitrogen, phosphorus, and potassium levels, but that is not nearly the whole picture. There are other, secondary elements that play a big role in keeping your plants happy and healthy, like iron, magnesium, copper, zinc, and boron (to name just a few!).
Most of the amendments on the market will have an analysis of what elements the amendment provides. It’s important to note these in order to correct deficiencies accurately. Take caution not to add too much of an element. Let’s take sulfur as an example; Epsom Salt contains 9.8% magnesium and we usually think of this to correct magnesium deficiencies, but there’s also 12.9% sulfur in there! Now look at gypsum; 29.9% calcium and 18.5% sulfur. If we were to use these products to correct calcium and magnesium, yet the soil showed adequate or even excessive amounts of sulfur, we would be doing damage to the soil. It’s ok to correct deficiencies over several growing seasons; it can be more difficult to correct an excess or toxic amount of an element.
One of the other very important keys to successful organic gardening is maintaining a healthy life balance in the soil (bacteria, fungi, protozoa, nematodes, and arthropods). Life in the soil should really be considered as an amendment in itself, because without it, your plants won’t be able to access the fine amendments you just applied. Many amendments are water-insoluble, meaning they can’t be readily absorbed by the plants just from dissolving in the soil with watering or rain. These amendments only become soluble when the various life-forms within the soil eat the amendments and poop them out (not to put too fine a point on it!).
So, how can we increase life in the soil? One of the best ways is to apply high-quality compost. Compost is concentrated with soil life! Do this every time you plant new crops by topdressing with about an inch around the plants. For perennials, apply once they begin growing and maybe again just before blooming. Another way to maintain healthy life is to protect your soil by keeping it covered with mulch (whatever your choice may be). Much of the life exists in the top 3 to 6 inches of soil. When we pull back the mulch layer, we want to see healthy populations of insects, worms, and even feeder roots of the crops currently growing. The mulch also holds in moisture, the other key to maintaining healthy levels of life in the soil. If soil dries out, we lose a lot of the biology. This is why irrigation can be important.
Once you are ready to amend, consider your current soil. If you can avoid tilling amendments in, do that. You can simply top dress and work into the top layer of soil, trying not to disrupt nature’s efforts at setting up biology. If you are working with poor clay soil, use this opportunity to till in amendments and compost. This will give you a jump start to building the soil, but then avoid hard tilling moving forward.
Here’s a few common amendments to get you started:
We love to talk soil at Fifth Season, and we are happy to help you figure out how to build your soil environment so that your plants can thrive. Just come on down and see us if you have any questions or are looking for some advice. Happy growing, y’all!