Do you ever wonder why some plants grow better in certain soils while others seem to struggle when it comes to producing leaves, flowers, or fruits? You might be feeding them correctly, but fertilizers aren’t the only factors in cultivating healthy plants. In this article, we’ll explore why soil pH affects the overall growth of your plants, how to correct the pH level, and how to maintain it.
The Main Reason for Needing to Know Your Soil pH
The secret to any flourishing garden is the health of its soil, which includes the pH level. This refers to the level of acidity or alkalinity of the soil. The pH scale ranges from 0 to 14, with 7 considered to be neutral. Soils with pH levels below 7 are considered acidic and soils with pH levels higher than 7 are deemed alkaline.
When the soil is too acidic, certain plants may perish from it. When the soil is too alkaline, other plants may not grow as well. Most plants thrive in soils with a pH range of 6.5 to 7.0, although there are some that really thrive in more acidic or alkaline soil.
Balanced Nutrient Availability
At 6.5 on the pH scale, most nutrients are available for the root systems of the plants to absorb. This pH level means that the environment is more conducive for plants to receive their required amounts of essential nutrients and trace elements to help them grow healthier and stronger.
If the pH level of the soil becomes too acidic, certain nutrients can become toxic, whereas others become less available. Excess aluminum and manganese content in the soil can cause plants to become deformed.
Phosphorus, in the same acidic environment, can react with iron and aluminum and become inaccessible to plants. At the same time, beneficial soil bacteria will not thrive in soils with acidic pH levels.
When the soil becomes too alkaline, certain nutrients become unavailable as well. Copper, iron, manganese, and zinc are some of the vital elements to overall plant health. This is why evergreen plants perform poorly in soils with high levels of alkalinity. Phosphorus, in particular, becomes inaccessible in alkaline soil. It requires the perfect range of 6.5 to 7.0 on the pH scale to become available for plants to absorb.
Adjusting the pH Level of Your Soil
There is only one way to determine the soil pH in your garden, a soil test. This will give you the exact makeup of your soil and where it lands on the PH scale. Depending on the test, it can also tell you about key nutrients in your soil and their levels.
You can pick up a soil ph tester fairly cheaply which will give you accurate results. There are also various services where you can send your soil in to get tested. These are often a bit more accurate, and can give you additional information on your soil makeup. Once you’ve determined your soil PH level you can take the steps to correct it if needed.
How to Fix Overly Acidic Soil
If you discover your soil is too acidic, you can neutralize it by adding lime. The exact amount of lime amendment will depend on the result of your soil test. Not all liming materials are the same, however. There are two major types that you can use, depending on the soil test results.
Acidic soils with high levels of magnesium will require calcitic lime amendments. These are mined from natural deposits of limestone and ground into fine powder. Sometimes, calcitic lime is called agricultural lime or aglime. This limestone amendment adjusts the pH level of your soil while supplying it with calcium.
For acidic soils showing signs of magnesium deficiency, you’ll need to add dolomitic limestone. This soil amendment is similar to calcitic limestone, except that it has magnesium content. Look for pelletized dolomitic limestone amendments as they are easier to use and apply. Aside from a more uniform coverage, you also get to use less compared to crushed dolomitic limestone.
The general rule of thumb when applying this soil amendment is 1:10. For example, if your soil test result recommends using 100 pounds of crushed limestone amendments, you can use 10 pounds of pelletized limestone as an alternative.
How to Fix Overly Alkaline Soils
Based on the soil test result, you can tell if your soil is too alkaline if it falls at more than 7.0 on the scale. Given that most plants do better in slightly acidic to neutral soil, you can amend overly alkaline ones by making them more acidic. You can do this by adding aluminum sulfate or elemental sulfur to the soil.
Aluminum sulfate works with the soil to change the pH levels quickly. While the results are rapid, there is a chance that the changed soil acidity can affect the roots of the plants negatively. When applying aluminum sulfate to the soil, delay planting for about a month so that the roots don’t get burned.
Elemental sulfur takes a few months to adjust the pH level of alkaline soils. It is better to work it into the soil rather than applying a top layer, especially during springtime. By doing so, soil microbes are exposed to more elemental sulfur, which these microbes eventually oxidize. The most popular form is in pellets as it is less likely to cause burns.
Maintaining Soil pH
With a soil test result in your hands, it’s actually easy to maintain the pH level of the soil in your garden. Simply follow the recommended amount of amendment applications to get the right level that you’re looking for.
However, amendments for acidic and alkaline soil can be eventually processed out of your garden. This means that your garden soil will slowly revert to its original pH level every few years. To keep the ideal pH level in your garden soil consistent, you should run a soil test every four to five years and amend it as necessary.
Plants that Love Acidic Soil
Here are some plants that prefer soils with 5.5 to 6.5 pH levels:
- Sweet potatoes
- Bell peppers
- Chili peppers
- Parsley
- Carrots
- Cucumbers
- Tomatoes
- Squash
- Broccoli
- Turnips
- Parsnips
- Potatoes
- Beans
- Oregano
- Sage
- Garlic
- Basil
- Spearmint
- Blueberries
- Cranberries
- Elderberries
- Raspberries
- Apples
- Rhododendrons
- Azaleas
- Gardenia
- Magnolia
Plants that Love Alkaline Soil
Here are some plants you might want to grow in alkaline soils:
- Asparagus
- Brussels Sprouts
- Cabbages
- Kale
- Collard Greens
- Leeks
- Marjoram
- Peas
- Rosemary
- Thyme
- Flowers
- Anchusa
- Borage
- California Poppies
- Lavender
- Forsythia
- Hydrangeas will turn pink in alkaline soil
- Lilac
Understanding Soil PH
Understanding your soil PH is crucial to a successful garden. Having the wrong levels can be harmful to your plants, and lead to less than stellar blooms or harvests. Luckily, it’s fairly easy to test and correct soil PH issues. Armed with the above information, you’re well-equipped to cultivate the perfect soil for any plant in your garden.
