Understanding Your Garden’s Soil
The novice gardener may not fully appreciate how soil is a vital component of a healthy garden. And with the exception of hydroponic gardening and a few other select gardening methods, a successful garden starts with having good 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 plant you wish to place in your garden, you will need to vary the ratio between those six soil components. Before we learn about the ratio, lets learn about each element of soil.
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 hold any nutrients from the soil as water passes through.
Sand is smaller than gravel but is not the smallest component particle in the mix. Nutrients tend to pass through sand, so soil mixtures 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.
Clay is the smallest particle in soil. Depending upon where you live, you may have a very low or very high level of clay in your soil. 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. Nutrients tend to bind to the clay as well, preventing plants from absorbing them.
Loam is not a soil particle per se, but rather it is a blend of soil particles. Loams vary greatly, from a sandy mix to a mixture with a higher clay content, which is fine, since not all plants require the same type of soil. The great thing about loam is that you can add one or more of the different soil particles until you get the desired loam consistency.
Organic matter, such as decomposing leaves or manure, can almost always improve soil conditions. For example, soils with a high clay content benefit from organic matter, since it 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.
Regularly add organic matter to your soil to help keep it 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. According to the “Southern Gardener’s Handbook” a 2-inch layer of mulch may help reduce water loss up to twenty percent and also keeps soil temperatures 5 to 10 degrees cooler.
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.
Commercial fertilizers list the ratio of each macronutrient on the package. If you are fertilizing leafy greens or lawns, look for a fertilizer with high levels of nitrogen. Purchase fertilizers with high phosphorus levels for plants with major blooms.
Since plants will absorb nitrogen, phosphorus and potassium form the soil you’ll need to fertilize your soil about every year.
Generally speaking, it is best to water plants deeply and thoroughly rather than frequently with less water. Watering plants thoroughly actually uses less water because it allows them to grow deeper roots in 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), but it also allows the plant to dry off naturally which limits disease and mildew.
Now that you understand the basics components of soil, you should be able to eye-ball what a good mixture of soil looks like-you should be notice some sand, silt, clay, gravel and organic matter in your soil. Generally speaking, dark brown or black soil has a lot of nutrients. Two other easy ways to distinguish good soil is how quick water drains from it (standing water is a bad indication), and texture (good soil will crumble easily when squeezed).
If 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, you can test the soil yourself with an at-home kit (or simple DIY test) or send some samples to a local cooperative extension or soil testing company. Generally speaking, you’ll start with gathering samples of your soil from around your garden, digging down about 4 to 6 inches. Remove any non-organic matter and break up any large pieces of soil. Mix soil together from around your yard. Follow instructions on the package or website.
Most soil testing kits evaluate the overall pH of your soil. The term "pH" refers to the overall alkalinity of acidity of soil. The pH scale ranges from 1 to 14, levels below 7 are considered acidic soil, levels above 7 is considered alkaline.
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.
Consider starting your own compost bin to enhance your garden’s soil. Compost uses vegetative scraps and other normal yard waste, so composting not only benefits your garden, it also helps eliminate waste unnecessarily thrown into the garbage.
Southern Gardener’s Handbook by Troy B. Marden (2014)