Balancing Act: Understanding the Ups and Downs of pH

By Cory Hughes
Published: March 27, 2020 | Last updated: May 4, 2021 10:34:57
Key Takeaways

The best growers have the basics of horticulture down pat. One of the most important basics is understanding pH. To get the most out of your plants, follow our expert's advice on balancing pH in your garden.

One of the first things you should do when starting your journey toward a green thumb is to truly understand the importance of pH—or, potential hydrogen, which refers to amount of hydrogen ions in the soil—and the impact it has on your garden. Learning how to manage your pH to get maximum results is one of the primary building blocks of a well-rounded education in horticulture. Knowing the right pH is essential in growing happy, healthy plants.


What is pH?

The pH of your soil is the measure of its acidity, falling somewhere on a 14-point scale. For example, water has a neutral pH of seven. The more acidic the substance, the lower the number on the scale. The more alkaline, or basic, the higher the number.

Plants require varying levels of pH to survive; however, the vast majority of them fall between 5.5 and 7.0 on the scale. Trying to grow plants in a pH that is out of their healthy range will cause you nothing but trouble. So, why is it so important to make sure your pH is dead on?


Read More: Measuring Up: Meters and Tests That Can Help Your Garden

Levels outside the normal pH range can have a direct impact on the nutrient bioavailability of the soil. When that happens, your plants simply won’t get the essential nutrients they need, no matter how much you feed them.

If you are using traditional soil, feeding it with the wrong pH has detrimental effects on the beneficial microbes and bacteria that are an essential part of the ecosystem. These microbes convert elements in the soil into a form more readily absorbed by the root system. If pH levels are too alkaline, it will result in an ineffective absorption of certain nutrients like phosphorus and manganese.


If the pH is too acidic, it will cause a buildup of aluminum and iron, which will interfere with nutrient absorption. In the end, if you want a lush, green garden, balancing your pH is a must.

Dialing in Your Garden's pH Levels

How can you change the pH of your soil in your home garden to get it right where you want it? First, you need to determine what the actual pH of your soil is. The easiest way to determine pH is by using an electronic pH meter. Just stab it into your soil at an angle and it will let you know where your pH is. If it isn’t where it should be for the plants you’re are growing, there are a number of ways to bring your pH back to within range.


If your pH is coming out hot, meaning it’s too high, you could try adding organic matter to the soil. By adding organic material, whether animal or plant waste, you are turning your soil into a smorgasbord for the bacteria and microbes that play a vital role in your garden’s ecosystem.

Beneficial microbes including bacteria and fungus play an essential role in your plant's ability to ingest nutrients. They break down organic material and convert nutrients into a form that your plants can more easily absorb. In the process, the microbes create an acidic byproduct that will, over time, lower the overall pH of the soil. Adding organic material to the soil is a tried-and-true method, however, its effects are more long-term and would not be good for quick fixes.

Read More: Beneficial Microbe Populations in the Indoor Garden

pH Up, pH Down

If you are looking for a faster way to condition your soil and bring the pH down to range, there are a couple of fast-acting solutions. One of the best and fastest methods is using aluminum sulfate. Aluminum sulfate is non-toxic to plants in limited amounts and will instantly bring down the pH of your problematic soil.

If you are looking to treat your soil before planting your garden, make sure to measure it out and do the right calculations before you start applying. As a general rule, for every 0.5 drop in the pH scale you wish to achieve, you will need 0.6 pounds (275 grams) of aluminum sulfate for every 10 square feet of soil.

Using a good pair of gloves, evenly spread the aluminum sulfate around your garden. It will lower the pH of the soil as it dissolves. If you need to lower the pH of a single developed plant, you can target the area by adding a quarter cup of aluminum sulfide to a gallon of water and apply.

Raising the pH of your soil is just as easy. If you find that it is too acidic, all you have to do is add a base. One of the more popular and easily accessible bases is lime. Not only is lime an excellent supplement for increasing the pH of the soil, but it also provides an additional source of calcium and magnesium.

Adding lime also increases aeration and airflow and increases water penetration in soil that may have been damaged by low pH. Lime used in gardens comes in a variety of forms, most commonly powder and pellets. Powder is most effective, with pellets being used for long-term shifts in pH as it takes much longer for pellets to dissolve. To raise the pH of 100 square feet of medium density soil one degree on the pH scale takes, on average, 6.5 to seven pounds of lime.

Sandier soils require closer to five pounds and harder, more dense soils require as much as eight pounds per 100 square feet. When using lime to increase pH, make sure to thoroughly water to ensure maximum dissolution. Note, however, it will take some time before you see a noticeable change in the pH, most likely about three to four weeks.

If you need a faster way to increase your pH, you can try using potassium carbonate. A staple in the wine industry, potassium carbonate is a fine powder that almost instantly dissolves in water. This makes it ideal for application through irrigation. As opposed to lime, which takes time to dissolve and saturate, potassium carbonate is much more easily distributed throughout the soil in a short amount of time.

Read More: Boosting Your Harvest with Potassium Supplements

The result is a much faster pH adjustment to acceptable levels. By adding potassium carbonate to your soil, you are also supplementing elemental potassium that will help strengthen plant cell walls.

If your plants just don’t seem to have the lush green appearance you are looking for and you feel you’ve tried everything, is it possible that you’ve skipped some of the basics?

In football, it is said the best players are the ones who can run, throw, catch, and tackle. Horticulture is no different. The ones with the best gardens are the ones who know how to do the basics, like balancing your pH.


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Written by Cory Hughes | Commercial Grower

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Cory Hughes is a former police officer turned full-time commercial grower in Denver, Colorado.

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