Soil testing—primarily for pH levels and nutrients—is typically a first step in creating a healthy, beautiful landscape. PH levels can help you gauge which plants might do best for your soil (acidic vs. alkaline) as well as whether it’s necessary to amend your soil. Soil that is in a healthy pH balance is better able to pull and absorb surrounding nutrients to nourish plants, than soils that are extremely out of balance.
So what is pH? It stands for “potenz Hydrogen,” potenz meaning “the potential to be.” You may already know that pH is a scale measure of acidity to alkalinity. Typically measured from 1 (highly acidic) to 14 (highly alkaline) with a measure of 7 registering as neutral or balanced. So where does the hydrogen come in? Hydrogen ions in the soil (which is actually a kind of soil solution) determine the level of acidity. A lot of Hydrogen ions make for an acidic soil, where a low concentration of them makes for an alkaline one. On a microscopic level, Hydrogen emits a weak, positive electrical charge, allowing it to attach to negatively charged particles that contain nutrients for the plant to feed on.
Important to note, even a slight change in soil pH, say from 6 to 5 can make a difference since the scale is based on logarithms not arithmetic. So a pH level of 5 is actually 10X more acidic than that of 6, and 100x more acidic than that of 7, etc.
That said, most plants are fairly tolerant of a range in pH, anywhere from 6.0-7.5. Nutrients and minerals become available for plant roots to absorb when they’re dissolved in water. When pH becomes too acidic or alkaline, the minerals don’t break down as easily for the roots to uptake. When soil pH drops below 6.0, nutrients such as nitrogen, phosphorous and potassium become hard for roots to absorb. When it goes above 7.5, manganese, iron and phosphorous (again) is no longer easily available for root uptake.
There are numerous factors that affect soil pH; locale, rainfall amounts, soil texture—even home construction! You can find soil test kits at your garden center or contact your county extension office. You provide soil samples, a lab tests them, then gives you a reading of your soil’s pH level, nutrient balance, and soil density, along with recommendations on how to amend your soil (what to use and how much of it).
Soil too acidic? Adding limestone (called liming) is the common fix. Generally you’ll choose between two types of limestone; calcitic (calcium carbonate) and dolomitic (calcium-magnesium carbonate). You should only use the latter if your soil is deficient in magnesium as well as being acidic. Whether your soil is porously sandy or densely clay will determine how much lime you’ll need to add to affect a change.
Wood ash is a traditional liming material that contains healthy trace minerals in addition to calcium carbonate and phosphorous. However, because the microscopically fine particles are so quickly and easily absorbed by plants, it can be easy to over-do it. A sprinkling of your (cooled please!) fireplace ashes once every 2-3 years is sufficient.
Found out your soil is too alkaline? Powdered elemental sulfur will increase acidity, as will shredded leaves and coffee grounds. Some plants that are happier in slightly acidic soils include blueberries, azaleas, rhododendrons, potatoes and hydrangea. You can actually change the color of your hydrangea by controlling the acidity of the soil. Flowers will be pink in more alkaline soil, and blue in more acidic soil.
Another great way to ensure your soil is at an optimum pH level for your plantings is to call us here at Farmside Landscape & Design. We can provide you with a comprehensive soil assessment amend your soil properly for optimum nutrient uptake and create a landscape design that will thrive in your environment, so all you have to do is enjoy your beautiful yard.