Hydrogen, We all know it as a highly volatile gas, but it is also a necessary element for life and growth. After all, hydrogen and oxygen together make water — and we all know how important that is!
In it’s ionic form in the soil, the amount of hydrogen present can determine how well your plants are able to take up nutrients. Too little or too much and the soil will become a toxic environment that will poison the plants.
The amount of hydrogen in soil can be measured and expressed as potential hydrogen or pH. Wait! Come back! This is a science lesson, but I promise that I’m not grading anyone! And my apologies if I’ve awakened anyone’s high school science nightmares.
The pH measurement scale goes from 0 to 15. A pH of 7 is considered neutral. Anything less than 7 is considered acidic. Anything greater than 7 is considered alkaline. The pH of chromic acid, for example, is around 1. If you got a drop of chromic acid on your skin, it would burn like fire, and I speak from personal experience (but that’s another story). Sodium hydroxide (household lye) has a pH of around 13.5, which is highly alkaline. Garden soil is typically at a pH of around 6.6-7.0 — between slightly acidic and neutral.
So what does this mean for us and our plants? At a soil pH of less than 6, plants are unable to take up calcium, phosphorous, and magnesium. In addition, micronutrients such as zinc, manganese, boron, iron, and aluminum will become so readily available, that the plant will take up too much, resulting in a toxic condition. If the soil pH is too high, iron and phosphorous also become unavailable.
The ability of our plants to survive depends in part on their ability to take up nutrients from the soil, and they do it best if the pH conditions are favorable. This can vary from plant to plant, but the majority of our garden vegetable do best at a pH of around 4.5-8.0. Potatoes, for example, do best at a pH of 4.5-6.5 — a slightly more acidic soil than is preferred by asparagus, which grows best when pH is 6.0-8.0.
How do we know if our soil is the right pH for a successful garden? Well, the best way to find out is to test your soil. You can do it yourself with soil test kits that can be purchased at nurseries or online gardening catalogs. Or if you want more accurate results, gather a sample of your soil and send it to a laboratory.
So what if your soil pH is too high or too low? Can it be adjusted? Yes. If your soil is too acidic, you can raise it by adding in ground limestone. If your soil is too alkaline, you can lower it with sulfur — either elemental sulfur, or as part of a compound such as ammonium sulfate.
So if your vegetable crops didn’t do so well last year, it may be due to the presence — excessive or deficient — of those critical hydrogen ions.