Most people who begin gardening come to the project with some awareness that the pH (potential of hydrogen) of the soil is somehow important. But, the understanding generally stops there. Many of us, and we needn’t be ashamed as most of us are not chemists, can’t really define what pH is, let alone balance it. Even if we know that scientists use a strange scale to measure it, we may not know how exactly that scale works.

Let’s begin, then, with a simple explanation.  Measuring the pH of something, such as soil, is used to determine whether or not the substance is acidic or alkaline (or possibly neutral) and to what degree. In terms of soil, discovering the pH level, understanding what that means, and knowing how to adjust it can make the difference between a bountiful garden and one that is anemic.

In other words, for those looking to grow luscious gardens or for those struggling to do it, a better grasp of soil pH could make a huge difference.

How the pH Scale Works

The pH scale stretches from 0 to 14, with 0 being the most acidic measurement and 14 being the most alkaline.  Hydrochloric acid is especially acidic (0 on the scale) while ammonia is particularly alkaline (at roughly 11 on the scale). Seven is neutral, and pure water — pure being very important here — has this balance.

The scale is logarithmic — something with a pH of four is ten times more acidic than something with a pH of five and 100 times more acidic than something with a pH of six. In other words, as we get further away from neutral, the severity of acidity or alkalinity becomes — literally — exponentially more powerful.

How Soil pH Works


For the most part, at least in vegetable gardens, we want our soils to be mildly acidic, say between 6.2 and 6.8, but that isn’t to say plants won’t grow outside this range. Places with lots of vegetation and rain, such as forests or swamps, tend to produce acidic soils whereas places like deserts are more likely to be alkaline.

This happens for a couple of reasons. Water, when not pure, tends to be mildly acidic, especially when delivered as rain, and the decomposition process, as we see from litter on the forest floor, is also a little acidic. Forests help create rain and produce lots of organic matter. Deserts do not.

In terms of gardening, soil pH can have a huge effect on a plant’s ability to absorb nutrients. Too acidic (say below 5.0) or too alkaline (above 9.0) and roots are unable to access minerals even if they are present in the soil.

Testing the pH of Soil


There are some basic things, such as forest versus desert soil characteristics, that can help with assessing soil pH even before testing it. Pine and oak forest, such as found along the eastern U.S., will have acidic soils because those trees produce particularly acidic organic matter. In these cases, it’s reasonable to take an educated guess at the general pH. Mixing the soil with vinegar will react with alkaline soil and/or baking soda reacts with acidic soil, which can also provide a general direction.

But, for big garden investments, it’s advisable to test the soil. Home test kits are available at most hardware store or garden centers. The devices that have a meter atop a spike that is stuck in the ground are largely regarded as unreliable. Instead, look for the kits with litmus papers and a vial (swimming pool kits work as well). With regards to DIY home testing, this will provide a reasonable approximation.

Otherwise, the best idea is to send samples to a university lab or government agency, which will give you the accurate pH level, as well as the nutrient content of the soil.

Adjusting (to) the Soil pH

There are a few things that can be done to deal with whatever soil pH is in the garden. In general, adding organic matter — a well-balanced compost or mulch —  will slowly move the pH level to that 6.5 ideal. Building raised beds will forego the problem as well, as the soil used to grow the gardens won’t be from the area. And, different plants perform differently in different soils. For example, berries generally love acidic soil, whereas asparagus can do with a bit of alkalinity. So, gardeners could just choose the plants best suited for the soil.

On the other hand, adjusting the actual pH level is simple as well. Acidic soils can be brought closer to neutral by adding lime, and alkaline soils can be moved towards a pH of 7 be adding sulfur. These can be sourced easily at garden centers, and there are plenty of natural sources to be had. In other words, an organic garden is still well within reach.

The pH Balance

Perhaps the most important thing to remember when dealing with pH issues is that there is always a solution, and the point is to optimize what’s there to be worked with. A pH reading is merely the information needed to make wise choices for the garden.

Lead Image Source: Pixabay