When it comes to your plants, selection of soil or growing medium is often overlooked. It is important to understand that selecting a growing medium is important to your plants’ success, so make sure you know what materials were blended into the mix you are purchasing. When the job you’re undertaking is smaller many people feel it is easiest to purchase a bagged soil mix.
Many nurseries carry soil mixes that they have blended themselves, or that they have obtained from a local supplier. You can find bagged soils packaged by national companies, but being a national brand doesn’t make them better than locally produced ones. If the job is on the larger scale soil companies sell blended soil mixes by the cubic yard and depending on the size of your order they will deliver them, or you can go directly to the company and pick it up yourself.
It is important to know what types of organic matter are added. Composted organic matter will often include manure, stable sweepings, bagasse and rice hulls just to name a few. Composted finely ground pine bark is also an excellent addition to increase drainage.
Be cautious with soil mixes. Many of them contain fly ash, which is essentially powdered charcoal to make them look black. They do this because gardeners generally associate black with fertile soil. The ash is for show only and adds nothing to improve the soil. It is better to purchase soil mixes that get their dark brown color from the addition of quality composted organic materials such as those mentioned above.
The company also should be able to tell you the typical levels of several major nutrient elements in its mix, including potassium, phosphorous, calcium and magnesium. Knowing the salts level is also helpful as high levels of salts are a problem for plants and can be toxic.
It is also good to include soil amendments like sand. You might intuitively think sand doesn’t make sense in a garden, and why would it, there isn’t much growing on your local beach. However, sand adds drainage and can break up heavier soils. Too much sand won’t be able to hold enough moisture, but 10% or so of sand into a soil mix can be a great additive.
Other amendments like peat and coir (composted coconut husks) can loosen soil and hold moisture. Some potting media are composed entirely of coir or peat. Some will have some fertilizers added. This cannot be very much or it would burn your roots initially. Therefore, you must understand that any fertilizer added must either be in the form of slow release which may last 3 – 6 months or a soluble form that is likely to be consumed by the plants in 3 – 6 weeks.
New soils often get better with age, and gardeners will talk about soil mixes “mellowing” over the first six to eight months after they are put in place. Whether improving existing soils through bed preparation or using soil mixes in the garden, never overlook the importance of the soil to the health, appearance and productivity of the plants you grow.
University of Maryland recommends testing turf and garden soil every 3 – 4 years. A basic soil test that gives readings for soil pH, phosphate, potassium, calcium and magnesium levels is sufficient for most home gardeners.
A basic soil test will tell you some important things about your soil that you cannot determine just by looking at it, smelling it, and feeling! And, it can save you money: less fertilizer used based on soil test results, and increased fertilizer efficiency by getting soil pH in the correct range.