Gardening is a fulfilling, enjoyable, and even meditative experience that makes hobbyists and enthusiasts around the world feel more connected to their landscapes. However, for a practice that feels wholly intuitive and based in the natural world, you’d be surprised to find out the crucial role that certain scientific concepts, like pH, play when it comes to its success.
Here are 5 reasons why soil pH is so important:
- Soil pH affects how many nutrients reach your plant.
- Different plants prefer different pH levels.
- pH allows garden plants to reach nitrogen sources.
- Nutrient deficiencies can be a direct result of soil pH.
- pH value can affect the level of bacteria.
In the following sections, I’ll dive into what soil pH is and the reasons why it can be so essential to your garden. I’ll also provide you with some ideas on how to test your soil pH and the best ways to fix it in the instances when it’s off.
1. Soil pH Affects How Many Nutrients Reach Your Plant
The first and most important reason why your soil pH is so important is that it affects how many nutrients reach your plant. I’ve briefly mentioned this correlation in the previous section, but let’s dig deeper (pun intended) into why this is.
Soil pH affects the availability of nutrients within your soil, and as we know, plants need nutrients to grow and thrive. Your plants may need some combination of the following essential seventeen nutrients:
- Carbon
- Phosphorus
- Magnesium
- Boron
- Potassium
- Manganese
- Chlorine
- Copper
- Molybdenum
- Calcium
- Hydrogen
- Sulfur
- Calcium
- Oxygen
- Nitrogen
- Iron
- Nickel
Now, compounds like hydrogen, carbon, and oxygen are naturally received by plants through the air. However, the other fourteen nutrients typically come from the soil we use in our gardens. This is why rich, nutritious soil is so important, it’s the plant-world equivalent to a well-balanced diet.
Some plants do prefer more acidic or more alkaline soils. Regardless, the pH determines the amount of the nutrients in the soil your plant can get to. Even if your mixture is rich in nitrogen, but the pH is strongly acidic, your plants won’t be able to get to it.
What Is Soil pH?
Soil pH sounds like a scientific term and may remind us of rainbow-colored testing strips in high school science class. However, gardening is connected to science more than you’d think, even if we don’t have to wear a lab coat and goggles.
Generally speaking, your soil pH needs to be between 6.0 and 7.0 for most common gardens, with 6.8 being ideal for crop production, but what does that mean?
Soil pH is the measure of acidity in your soil. Measuring the pH level will tell you if your soil is acidic, alkaline, or neutral. Different nutrients live within different pH’s, so determining your soil’s acidity is necessary for a thriving garden.
Basically, substances can either be acidic, alkaline or somewhere in between. Think about examples in your life outside of the garden that are acidic–like orange juice or lemonade.
These substances can wear down on your teeth if you drink too much or cause acid reflux in your stomach.
On the other hand, alkaline substances like milk or water might help your mouth cool down after eating something too spicy.
In the garden, acidity and alkaline work similarly yet in different ways. The pH level of your garden determines what nutrients will be present. A slight acidity is good for some plants, while other plants need more alkaline soil. This video helps to explain what this looks like in your garden:
Though Brian and Darren from AgPhD talk about soil pH in the context of farming, the same principles remain true in even the smallest of gardens. You need to know your soil’s pH level if you want to continue nurturing your garden, and it may give you some insight into why you might be having problems.
Something to remember when talking about soil pH is the pH scale. 7 may seem like it’s getting pretty high in acidity or alkaline levels, but 7 is neutral. Anything below 7 indicates an acidic environment, and anything higher than 7 indicates alkaline soil.
2. Different Plants Prefer Different pH Levels
As I briefly mentioned above, some plants prefer different pH levels. Even if you understand that pH makes nutrients available for your plants and you follow the 6.8 rule, you may be stumped to find that some of your plants aren’t taking to your soil. Again, even soils may have different preferences.
The University of Clemson gives us a pretty good rulebook regarding what we should plant in what pH soil. Their College of Agriculture, Forestry, and Life Science suggests a more acidic soil, between 5.0 and 5.5, for plants like azaleas, rhododendrons, blueberries, and conifers, as they prefer higher acidity in their soils. For crops like vegetables, grasses, and ornamentals, you’ll want to use a little less acidic soil, somewhere between 5.8 and 6.5.
If your soil is more alkaline, you’re better set to plant quite a few vegetables. You can successfully grow these vegetables in alkaline soil:
- Asparagus
- Beans
- Beet
- Brussel Sprouts
- Cauliflower
- Garlic
- Kale
- Pea
- Pumpkin
- Spinach
- Tomato
Having said that, these plants won’t successfully thrive in a pH level much higher than 7.5, just slightly above neutral.
3. pH Allows Garden Plants To Reach Nitrogen Sources
As I’ve mentioned above, 6.8 seems to be the ideal pH for most gardens. But why is this? Grow Appalachia uses a great metaphor in this video, where they explain that reaching nutrients in the soil is kind of like reaching for food in the middle of a giant table:
Basically, without a monitored pH, your plants won’t be able to gather all of the available nutrients. Nutrients are present and obtainable by plants in specific pH values. Most of the compounds are available at somewhere between 6.0-7.0 pH, with 6.8 being the go-to for most gardeners.
Therefore, even if your garden is nitrogen-rich but the pH is very low, your plants won’t be able to tap into its nitrogen sources and will become nutrient deficient. I’ll touch on nutrient deficiencies a little more below.
4. Nutrient Deficiencies Can Be a Direct Result of Soil pH
Nutrient deficiencies are a gardener’s worst nightmare. Unlike watering or sunlight, where you can just water less or add a sunshade, there’s little a gardener can do quickly to fix a nutrient deficiency. Additionally, there are seventeen essential nutrients for plant growth, and figuring out which one your plant is lacking can feel like finding a needle in a haystack.
Deficiencies can directly result from soil pH, especially if you’ve already tried feeding your soil everything it needs, but it seems as though it’s just not getting it. Finding soil rich in nitrogen or phosphorus is a great way to help with plant nutrient deficiencies, but not if the soil pH isn’t right in the first place.
If you’re sure that your soil is rich in nutrients, you may want to scan it to determine its pH level. Plants with nutrient deficiencies may rot, lose color, change colors, wilt, or display any number of other symptoms. While these may just result from a nutrient-absent soil, it can also be a sign that your soil pH is off and plants cannot get the nutrients they need.
5. pH Value Can Affect the Level of Bacteria
The soil pH value can also affect the level of bacteria within the soil.
This is one of the lesser-known consequences of having an off pH balance, but there’s tons of research backing it up. As most gardeners already know, bacteria come in one of two categories: beneficial or damaging to your plants.
Some bacteria can only grow and thrive within a specific pH range, while others are resilient. Regardless, your pH level may affect how much bacteria is growing within your garden.
If you’re facing bacteria issues, this may be an indicator that adjusting the soil’s pH level might fix them. Funguses are pretty resilient in almost any pH level, but other bacteria may have trouble in more alkaline or acidic soil.
The soil’s pH level may fix the lack of healthy bacteria in your garden, as well. Washington State University found that the acidity of soil may impact the beneficial microorganisms within it that support the fertility and vitality of your garden.
How Can I Test My Soil’s pH?
Hopefully, by this point, you’re convinced of the importance of soil pH. pH determines the nutrients available to your plants, can affect bacterial growth, and prevent your plants from growing and thriving. However, unlike a waterlogged garden or a patch of soil dehydrated from the sun, figuring out what your soil pH is will take more than just a look.
To test your soil’s pH, you can use text kits, a meter, or send a sample into a lab. Each is a viable approach, but the best solution for you will depend on your budget and the size of your garden. Testing your soil pH will give you some insight into the acidity or alkalinity of your garden.
The three main approaches for testing your soil’s pH are:
- By meter
- With a kit
- Sending a sample to the lab
Each of these methods will tell you your soil pH, but only a few will give you information regarding what nutrients are missing in your soil, as well. For the purposes of soil pH testing alone, your budget is what should have the heaviest influence on this decision. I’ll expand on the three methods below.
Meter
A pH meter reads the acidity level of your soil and then displays it. The benefit of pH meters is that you only have to buy one, and they often come with hydration meter and sunlight meter options as well. They won’t be as accurate as a kit, though, and they won’t tell you what nutrients your garden lacks as a soil sample might.
To use a meter, you only have to stick the equipment into your plant, avoiding any roots. These eters can be found in garden supply stores, most chain stores, and the internet.
Kit
A soil pH kit is similar to what you remember of a pH kit from your high school science lab. The kits use a strip of paper or a plastic device to test your soil. They come with their own set of instructions, and each is different from the next, but you’ll generally add a sample of your soil to the device and add some water or a special liquid to test the acidity.
This video gives a visual demonstration of how to use a pH testing kit:
Soil testing kits can be found at your gardening center and easily found online.
Send a Sample to A Lab
Another option is to send a sample of your soil into a local lab. These results will be the most accurate, as labs use more intensive and expensive equipment to test the pH of your soil. They will also be able to test for other components, like nutrients or bacteria, in the same test.
To send your sample to a lab, you usually have to figure out where you’ll want to send your soil first. They will typically provide the bag and instructions for testing your soil samples.
How Can I Fix My Soil’s pH?
If you’ve tested your soil pH and found that your soil is leaning to one side of the scale or the other, you may be anxious to fix it. The process can be time-consuming, but there are no quick fixes for your soil pH.
You can fix your soil pH by using methods such as liming, wood ashes, or sulfur. You will first need to figure out if your soil is too acidic or alkaline and then decide how you’d like to combat the issue.
It’s important to follow instructions to a T, as doing too much of one of these methods might send your soil pH in the other direction.
Correcting soil pH may be more tedious and less straightforward than solving problems with watering or sunlight, but it’s definitely worth the time. Using limestone for highly acid soil is a common solution utilized by farmers and gardeners alike. Again, be sure not to overdo it with any of your problem-solving strategies, as doing so may send your soil to the other end of the spectrum.
You can read my other article on soil improvement here: How To Improve Soil Quality (The Ultimate Guide)
