Acidification is a process that lowers soil pH.
Soil can be alkaline, acidic, or neutral. The pH scale ranges from 0 (acidic) to 14 (alkaline), with (neutral) 7 in the middle. Soil pH dictates the availability of many nutrients to your plants’ roots.
Your soil can be packed full of important minerals, but the wrong pH can make it impossible for plants to reach that bounty. Unfortunately for my plants, my soil has a pH of 7.7 and very little iron. Plants need iron to absorb many other essential nutrients. By lowering the pH, or acidifying, my soil, I can make the iron more readily available. If you live in the Bay Area and want to grow acid-loving plants, you will probably need to acidify your soil. The infographic below shows the likelihood of any nutrient being absorbed, based on soil pH:
Which edible plants prefer acidic soil?
If all of your plants prefer your soil’s current pH, you are in luck. It’s really the easiest way to go. Most garden and landscape plants prefer a pH range of 6.2 to 7.3. Acid-loving plants include:
Moderately acid-loving plants that prefer a pH of 5.5 to 6.5 include apples, basil, carrots, cauliflower, corn, cucumber, dill, eggplant, garlic, melon, peppers, pumpkin, rhubarb, winter squash, tomato, and turnips. Since the Bay Area’s tap water supply tends to be alkaline, and our soil is also alkaline, we can profoundly help our plants by lowering the soil pH. Or, grow native and other plants that have evolved to prefer what we already have.
Factors of acidification
There are three factors that determine the amount of acid needed to lower soil pH. Some of this stuff gets deep in the world of chemistry, but I think I have sorted it out well enough. [If you understand these things better than I have explained, please educate us all in the Comments section!]
How to acidify soil
While using the above information will give you more accurate data, you can gently acidify your soil by applying elemental sulfur (S) in stages. As the sulfur oxidizes, it turns into sulfuric acid, acidifying the soil. Changing soil pH takes several months to accomplish and it tends to require regular monitoring and adjustments. Since soil pH is a function of geology and climate, it will be an ongoing process. Just be sure to read and follow the package directions.
Fertilizers and acidification
Nitrogen has a powerful impact on soil pH. The form of nitrogen you use makes a difference. To lower the pH of your soil, use ammonium- rather than nitrate-based fertilizers. Your blueberry plants will thank you.
You can grow a surprising amount of food in your own yard. Ask me how!