If you are new to gardening, or if you’ve always just had a brown thumb, then you need to know about soil pH. Why? Don’t you just plant the seed, water it, and then wait for the seeds to sprout? In simple terms, yes. If you want to get more out of your garden though there are many subjects you should be familiarizing yourself with. Near the top of the list is understanding soil pH. If your soil pH is off it can severely hinder the uptake of important nutrients by your plants resulting in smaller, unhealthy plants and low crop yields.
What Is pH?
pH, in scientific terms, is a measure of the available reactive hydrogen ions, in this case, in the soil. In layman’s terms, the higher the concentration of reactive hydrogen ions, the more acidic something is. pH is measured on a logarithmic scale from 0 to 14 with 7.0 being considered perfectly neutral. The lower the number on the pH scale, the more acidic a solution is, so stomach acid falls somewhere around 1 indicating it is highly acidic. Because the pH scale is logarithmic in nature every change of a point is actually a ten-fold change so if your soil pH is a 6.o and you apply enough limestone to raise it to 7.0 you have changed it significantly. To put it in a different perspective the human body attempts to maintain a pH between 7.35 and 7.45. A change in pH to 7.1 would be considered a medical emergency with possible coma or death consequences. When you begin measuring your soils pH make sure that you know where you are starting, where you want to end up, and how much organic matter or fertilizer it will take to get there.
Determining Your Soils pH
To correct the pH of the soil in your garden you will need to first purchase a soil sample kit or send off a soil sample to a state soil testing lab. You can find a soil analysis lab by googling “soil analysis labs in _____” and enter your state. I was not able to find a single consolidated list for all states. Average soil analysis tests run around $35. Your local ag extension can also likely help you locate a lab to test your soil.
Changing Your Soils pH
Now that you’ve determined the pH of your soil it’s time to use that new found knowledge to fix it and help boost your plants health. Most plants will tolerate a pH as low as 5.5 and as high as 7.5 and if you are in this range and looking to move slightly more toward a more neutral the recommended practice is to amend with organic compost. “Raising the organic matter content of soil will usually move the pH of both acidic and alkaline soils toward the neutral range….Finished compost usually has a near-neutral pH, so regular infusions of…..compost and organic mulches may be the only amendments you need to keep your crops happy and your garden growing well.” (Mother Earth News) If your soil is extremely acidic or alkaline, in addition to regular organic compost amendments, you may need to take specific steps to correct the soil.
For acidic soil: “The most common way to raise the pH of soil is to add pulverized limestone to the soil. Limestone acts as a soil acid neutralizer and consists of either calcium and magnesium carbonate or calcium carbonate. These are called dolomitic limestone and calcitic limestone respectively.” (Gardening Know How)
For alkaline soil: “Spread sphagnum peat moss over your garden plot in an even layer about 2 inches thick. Do this at the start of the growing season. Work it into the top 10 inches of soil with a garden fork or tiller/cultivator. Sphagnum peat moss is acidic, with a pH of around 4, which balances soil alkalinity. But it is expensive for large garden plots. Apply granulated elemental sulfur instead of sphagnum peat moss on large garden plots. Apply evenly at the start of the growing season at a rate of 10 pounds per 1,000 square feet. Reduce the rate by 33 percent for sandy alkaline soils. Elemental sulfur combines with rainwater and soil moisture to create mild sulfuric acid that balances alkalinity. Retest the soil at the start of the next growing season, and treat again if needed.” (Home Guides) “Add elemental sulfur (90 or 99% sulfur material) annually at a rate of 6 to 10 pounds per 1000 square feet of area. Elemental sulfur slowly oxidizes in soil to form sulfuric acid. Test the soil occasionally and stop adding sulfur when pH has reached desirable levels.” (Utah State University)
Understanding How to Apply This Knowledge
Before planting you need to determine what type plant you will be planting. This is where companion planting comes in. Plants that benefit one another when planted close by also have similar soil requirements making it easy to make the soil pH of certain beds within the perfect target range for those plants. As an example, blueberry bushes prefer very acidic soil in the range of 4-5 which would be far to acidic for most garden plants that prefer a pH more in the range of 6.0-6.5.
With fall upon us, now is the time to start amending your beds in preparation for the winter. Layering your beds with compost will allow them to “cook” over the winter so that you can maximize your garden’s potential next spring. Have a great day and God bless!