We tend to ignore it as new gardeners but soil is the key to healthy, happy plants. Find out how soil is formed, the basics of sand, silt, and clay, and use this simple DIY test to learn your soil composition.
If you want your soil analyzed, we shared our experience with home test kit versus a laboratory test here.
Soil is The Foundation
One of the hardest things to accept as a new gardener is how important soil is. It seems so unsexy compared to the allure of plants. But let me convince you otherwise. Especially since you can’t have one without the other.
It may only cover a few inches, or some cases a few feet, of the earth’s surface, but soil quality can make or break the survival of plants and everything that depends on it. And that includes us.
It’s the place where rocks and air, sun, living things, and water all come together to nurture new life. (Wow!)
If you’re lucky, you have soil and growing conditions perfect for your plants and never have to think twice about it. But, for the rest of us mere mortals, the sooner we focus on soil health as a fundamental part of gardening, the better our gardens will grow.
If I had paid attention to this when I was starting out, I would have avoided several years of struggle and frustration.
Garden Soil 101
Soil | The foundation of your garden. Know what you’ve got and provide only what it needs.
• Mulch | Add 2-inches of organic matter to protect soil, retain moisture, and gradually fertilize your soil.
• Leaves | Finely chopped fall leaves make excellent mulch.
• Compost: Decomposed organic matter providing nutrients for the garden.
• Potting Mix | Contains no soil: designed to optimize plant growth in pots.
• Seed Starting Mix | A lightweight potting mix for sowing seeds in containers.
• Soil pH | Knowing your level (which may vary) is informational, not a call to action. Most soils fall in the range of 5 to 8 and accommodate a wide range of plants.
What is Soil?
There are actually debates about the exact definition of soil.
The Soil Science Society of America (on their website) says
“Soil is a mixture of minerals, dead and living organisms, air, and water.”
And that’s good enough for gardening purposes.
Those combinations—minerals, organisms, air, and water— are not only different from place to place—but within your garden as well, and the mix changes over time. Nature is always changing and how we tend our gardens affects it as well.
Where Does Soil Come From?
Most of our soil is weathered rock.
It starts with rock below the soil. Over the course of hundreds or thousands of years, these rocks get broken up into smaller and smaller pieces—by changes in temperature, by wind and rain—especially acid in the rain, by glaciers, waterways, and ultimately by living organisms and plant roots. And that’s what becomes soil.
If you live somewhere that was covered by ice 10,000 years ago, that’s probably the case. We live on top of a sand plain, thanks (or no thanks!) to glaciers, so our sandy soil isn’t a mystery.
Soil can take centuries to form but little time to destroy.
New soil is always being created from rock, but it’s a very slow process. And it can vanish quickly, which is why we have to be careful. It can take centuries to replace and little time to destroy.
One teaspoon of soil can have over a billion living microbes. They are a vital component of fertile soils.
Nearly half the volume of soil is mineral and about half is pore space for air and water.
Tucked in there is organic matter—living or dead—making up less than 10 percent and often less than 5 percent of soil composition.
Yet, in just a teaspoon of soil there will be over a billion living microorganisms of various sorts.
We can’t see them but those billions of microbes in your garden are doing an incredible amount of work, providing nutrients and soil structure.
But, if you are familiar with problems like damping-off—a fungal disease that kills plant seedlings, they may also work against us.
Such is life.
Once you understand the life force at work with microorganisms, it’s clear that pesticides and herbicides have no place in our gardens.
Easy Soil Composition Test
Soil texture, which is formed by mineral particles, is divided into three groups based on their size (largest to smallest): sand, silt, and clay.
You’re almost certainly going to have some of all three in your soil.
This test is an unscientific way to view the proportions.
As small as we think sand is, the sand particles in your soil can be 40 times the size of the largest silt particles and 1,000 times the size of the largest clay particles.
I’ve been wanting to do this soil test for ages, just for fun, but the result of my test was so absurdly predictable I’m surprised the soil didn’t jump right out of the jar and say, I told you so! You’ll see what I mean.
- Clean 1 L / 30-ounce mason jar with lid (or any size jar)
- Garden soil
- 1T Dishwater detergent or water softener (optional)
- Dig an 8-inch deep x 4-inch wide hole in one of your garden beds.
- Fill mason jar 1/3 full with soil.
Mark the top of the soil line on the jar with a marker or piece of tape before adding the water.
- Fill rest of jar with water, leaving an inch or two at the top for shaking space. Mark the top of the water line as well.
- Add 1 tablespoon dishwasher detergent or water softener (optional).
I’m not convinced it’s needed but it’s mentioned in some tests.
- Tighten lid and shake thoroughly. Shake, baby, shake.
Soil Test Results
We’re simply looking to see the proportions of sand, silt, and clay in the sample.
Depending on the composition of your soil, the results may be obvious within minutes, an hour, and perhaps longer. I’ve only done it with my very sandy soil which settled quickly in under 20 minutes. Silt and clay are slower.
That mythological creature known as loam, which few of us have, but many of us dream of, is approximately 40% sand, 40% silt, and 20% clay.
Soil Test Layers From Top to Bottom
- Top: Water and miscellaneous organic and other matter.
- Clay: the lightest and therefore slowest particle to settle.
- Silt: The middle guy.
- Sand: The heaviest particle, settles on bottom of jar.
If you marked the original soil level in the jar, compare it to the settled soil now to see how much is left to go.
After an hour (or when it’s apparent that most everything has settled), use a ruler to measure your layers, excluding the water on top.
For example, if all of the layers together measure 6″, what portions of the total are sand, silt, and/or clay?
I guess I already spoiled my result several times: my soil is nearly 100% sand. Boo!
Just about any garden can benefit from amending soil as plants grow and take up nutrients but gone are the days of doing it blindly with synthetic fertilizers.
It’s a waste of resources and harmful to our waterways to use fertilizers that plants cannot take up. More is not more: they can only use what they need and only then if conditions are right.
Instead, consider gettering a proper soil test from an accredited lab to have a basic measure of your soil’s composition. But check first to see what sort of report they provide and if you could make use of it.
Our lab caters to farmers and the report and recommended amendments were difficult to translate into home garden terms. But I did find it helpful to know which components were deficient or plentiful as a starting point.
We also compared our soil lab test results to the same sample measured with a cheap home soil test kit. They’re just $20 (see it here on Amazon) but not worth the money if our experience is typical.
Overcoming Poor Soil
I regard soil improvements as a lifelong venture. My approach is to gradually build up better soil on top of poor soil, with minimal digging.
I add household compost and cover bare spots with wood chips about 2-inches deep. It takes many seasons but soil health can improve with the right inputs and time.
~Melissa the Empress of Dirt ♛