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Understanding Your Garden’s Soil

Lockridge is an avid reader who enjoys learning about beautiful garden plants. Among other things, she has worked with a florist.

Dark colored soil normally indicates healthy soil.

Dark colored soil normally indicates healthy soil.

What Is Soil?

The novice gardener may not fully appreciate how soil is a vital component of a healthy garden. Wit the exception of hydroponic gardening- which is done without soil mainly using the natural moisture in the air- most successful gardens require healthy soil.

Soil is made up of four basic components: gravel, sand, silt, and clay. Loam and organic matter, while not necessarily a type of soil, are two other important facets that affect overall soil health.

Depending upon the type of plants you wish to place in your garden, you will need to vary the ratio between those six soil components in order to meet your plants needs. Before we learn about the ratio, let's learn about each element of soil.

The Primary Components of Soil

There are six primary characteristics or components of healthy soil: gravel, sand, silt, clay, loam and organic matter.


Gravel is normally the largest particle in your standard soil mix. It is coarse and holds little to no water. Gravel has virtually no nutrients, nor does it retain any nutrients from the soil as water passes through it.


Sand is smaller than gravel but is not the smallest component particle in the mix. Nutrients tend to pass through sand, so soil mixtures that are heavy with sand tend to need more frequent fertilization.


Silt is a smaller particle than sand and is the primary component of proper soil. Silt is comprised of decomposed plant and/or animal matter, such as manure, leaves, and twigs. Unlike gravel or sand, silt retains moisture and nutrients. It also has the ability to trap air, which helps plants thrive.

This old Alabama road is composed of red clay.

This old Alabama road is composed of red clay.


Clay is the smallest particle in soil. Depending upon where you live, the soil in your garden may have a very low or very high levels of clay. Clay particles have jagged edges (visible only under a microscope) and are highly ionized, meaning they are positively or negatively charged and can bind together quite tightly. When dampened, the jagged edges of clay bind together so tightly that not even air or water can exist between the adjoining pieces. Because of the tight bonds, nutrients tend to bind to the clay, preventing plants from absorbing them.


While loam is not a soil particle per se, it is rather the blend of soil particles, and can vary greatly, from a sandy mix to a mixture with a higher clay content. Since not all plants require the same type of soil, you can add one or more of the different soil particles until you get the desired loam consistency for your specific plant needs.

Organic Matter

Organic matter, such as decomposing leaves or manure, almost always improves soil conditions. For example, soils with a high clay content benefit from organic matter, since the organic matters helps to break up the tight bonds and allows air and moisture to get into the soil. Sandy soils also benefit from organic matter, as it helps to improve water retention for the plants. Most plants benefit from the regular additional of organic matter, as it helps to keep plants in peak condition.

Mulch is a form of organic matter that gardeners often place on top layer of the soil. More than just a decorative feature, mulch helps the soil retain moisture instead of it evaporating. According to the Southern Gardener’s Handbook, a 2-inch layer of mulch may help reduce water loss up to 20 percent and also keeps soil temperatures 5 to 10 degrees cooler.

Amending Soil: Fertilizing Basics

There are three basic nutrients that all plants need: nitrogen (N), phosphorus (P), and potassium (K). Since plants naturally deplete the soil of these macronutrients, you’ll need to fertilize your soil well and often if you want healthy plants year after year. Plan on fertilizing every year.

When shopping for fertilizer consult the product packaging for the ratio of each macronutrient. Purchase a fertilizer with high levels of nitrogen for lawns. Purchase a fertilizer with high levels of phosphorus levels for plants with major blooms.

Watering Basics

Generally speaking, it is best to water plants deeply and thoroughly rather than frequently with less water. Although it may seem counter-intuitive,watering plants thoroughly actually uses less water because it allows plants to grow deeper roots into the soil, and deep roots use water more efficiently.

Water plants during the cooler times of the day, such as in the morning before sunrise. Not only will your plants actually receive more of the water (since it won’t evaporate in the heat) but watering plants when it is cool outside allows the plant to dry off naturally which limits disease and mildew.

Plants can absorb water best during the early morning hours.

Plants can absorb water best during the early morning hours.

Evaluating Soil

Now that you understand the basics components of soil, you should be able to easily determine what a good mixture of soil looks like. Healthy, balanced soil will contain elements of sand, silt, clay, gravel and organic matter. Generally speaking, dark brown or black soil has a lot of nutrients, whereas light colored soil is nutrient depleted.

Another way to distinguish good soil is notice how it reacts with water. For example, standing water on soil indicates a drainage issue, whereas good soil will "crumble" easily when squeezed.

If you follow the tips listed above, but you still aren’t sure if you have adequate soil, consider testing it. There are a few options you have when it comes to testing soil, such as purchasing an at-home kit or sending samples to a local cooperative extension or soil testing company. Most testing instructions require that you gather soil samples from various locations around your garden, digging down about 4 to 6 inches. Remove any non-organic matter and break up any large pieces of soil, then mix all your soil togethers to get a good overall sample from your yard.

Most soil testing kits evaluate the overall pH (or the overall alkalinity or acidity) of the soil. The pH scale ranges from 1 to 14, levels below 7 are considered acidic soil, levels above 7 is considered alkaline.

Depending upon your soil's pH you may need to reconsider what you plant in your garden. Not only does pH help determine overall what might be successful in your garden, it might also determine the color of blooms in your garden too! Both hydrangea and azalea blooms are affected by a soil's pH.


Don’t try to amend soil with a high content of clay by adding more sand, as this may just result in a concrete-like mixture. Be sure add equal parts organic matter and sand to clay to help create a good overall balance.

Consider starting your own compost bin to enhance your garden’s soil. Since compost uses vegetative scraps and other normal yard waste, it not only benefits your garden, it also helps eliminate waste from unnecessarily being thrown into the garbage.


Benefits of Composting

How to Check Your Soil's pH Without Purchasing a Soil Testing Kit

Southern Gardener’s Handbook by Troy B. Marden (2014)

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


Liz Westwood from UK on June 03, 2019:

This is a useful guide for novice gardeners.

Jennifer Jorgenson on May 31, 2019:

This is an excellent article. Soil is so important. I find that each new gardening year I go back to these basics. Thanks for putting it all in one place! I will definitely be using this as a reference.