Altering soil pH
Soil pH is, for the most part, a function of your local bedrock material. This isn’t going to change any time soon. What you can do is integrate certain practices in to your normal gardening routine that will temporarily alter soil pH. East of the Rocky Mountains, soil tends to be more acidic; west of the Rockies, soil is more alkaline. Traditionally, acidic soil is treated with lime, to bring is closer to a neutral pH. If your soil pH is too low (like much of the Bay Area), you can acidify your soil with sulfur. Some people claim that adding peat moss or pine needles to the soil can increase its acidity, but research has not shown this to be true. Unfortunately, altering pH takes time and repetition to see any results.
Also, it is more difficult to alter the pH of clay soils, commonly found in the Bay Area. Once you begin treating your soil, it is important to continue monitoring pH levels.
In the long run, a soil pH of 6.0 to 7.0 will help your plants become healthier and more productive.
Soil pH can make or break your plants' ability to absorb nutrients and thrive.
What is pH?
Everything is existence is either acidic, alkaline, or somewhere in the middle. The pH scale is a simplified version of an algorithmic equation that measures the number of hydrogen ions in a specific quantity of a material in solution. The scale ranges from 0 to 14, with lower numbers indicating acidity and higher numbers indicating alkalinity. In the middle; 7.0 indicates neutral.
Testing soil pH
Soil pH can be tested with an over-the-counter product found at all garden supply stores. Testing the soil will tell you if your soil is neutral (7.0), alkaline (greater than 7.0) or acidic (less than 7.0). While over-the-counter pH tests are accurate enough, other soil tests available from retail outlets are not. To get your soil tested, and I urge you to do so, use a local, reputable soil test lab.
pH and nutrient availability
Plants grow best when they have access to all of the nutrients they use to grow and reproduce. At certain pH levels, some nutrients become unavailable. At the same time, soil microbes, which help plants absorb nutrients, are also restricted by certain pH extreme. Also, some plants, such as blueberries, prefer more acidic soil. Using the chart below, you can see that more nutrients are available, and there is greater microbe activity, when soil pH is between 6.0 and 7.0. Most plants can survive in soil pH from 5.2 to 7.8, but the narrower range allows plants to thrive.
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.