Plants a bit blah? A chemistry lesson on hydrogen might bring them back to life
The power of hydrogen is not often discussed among gardeners unless you are a chemist. Commonly known as pH, it measures of the number of hydrogen and hydroxyl ions in the soils. But enough with the chemistry lesson.
The measure of the acidity or alkalinity of soil, pH, is expressed on a numerical scale. The scale ranges from 0 to 14, with 0 being the most acidic and 14 the most alkaline. pH value of 7 is neutral, neither acidic nor alkaline.
Soil pH is essential for gardeners as it influences how the soil interacts with plants. Most importantly, it regulates the availability of nutrients for plant growth. Nutrients are bound tightly to the soil particle and unavailable to the plant if they are either too high or low. The result is poor growth.
So pH plays a vital role in regulating soil microbe activity as well as decreases leaching nutrients and the toxicity of any excess nutrients. The pH influences how clay partials are bound, affecting how easy it is to till garden soil.
There is no way to determine the soil pH level by looking at it. It’s influenced by how the soil was formed over millions of years and even shorter-term gardening practices. Soil testing or pH meters are the best ways to determine the level.
Because of the parent materials, soils in the Kansas City region are generally more alkaline, with a pH value of 7 to 7.3 being the most common. This number is based on thousands of soil tests done over two decades at Johnson County Extension.
Plants tend to grow best at a pH level slightly acidic, between 5.5 to 7. There are exceptions, as acid-loving plants such as azaleas, rhododendrons and blueberries prefer nutrients available at lower levels.
It’s difficult to change pH due to the soil mass. Changing should only be undertaken based on the recommendations of a quality soil test. Without the baseline, making changes would be akin to “shooting in the dark.” You never know what you will hit.
Lime is used to raise the pH, adding more alkaline. Sulfur is added to lower the pH, making the soil more acidic. Since Kansas City soil tends to be high, additional lime is seldom required.
Many gardening books recommend adding lime as the authors garden in areas with lower pH levels. Lime is widely available at garden centers, while finding the recommended pelleted sulfur can be more challenging.
Changing the pH in the soil is a slow process as the sulfur or lime must be worked into the rooting zone up to 6 inches deep. Take a soil test before planting, allowing for any adjustments to be incorporated. Once a garden area is planted, the change in soil pH is slow to take effect as the required materials must be applied at lower rates not to burn plant growth.
The power of hydrogen is more than a number. A correct pH unlocks your soil potential. Now is time to test your soil, determine your pH, and formulate a plan for success in your garden.
Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Have a question for him or other university extension experts? Email them to garden.help@jocogov.org.
