The right soil pH is crucial for the health of your plants. It is one of the primary things that can determine how well your plants absorb the nutrients they need to survive and thrive. Most plants do best with a pH between 6.0 and 7.5, but research the plants you are growing specifically to see what they need. A soil test can help you learn your current pH levels.
How to Alter the pH
Once you know if you need to increase or decrease the acidity, you can take steps to organically alter the pH in your soil. Here, we will look at what to do if your soil is too acidic, or, in other words, what to do if you need to raise the pH.
- Test your soil. This will help you determine how much you need to raise the pH. You can get your soil tested through your local extension office or with a soil test kit you can buy at most garden centers.
- Determine what you will use to increase soil pH. You have a couple of options to organically raise the pH in your soil.
You can use limestone, which is one of the most common ways to raise pH. The amount you use will vary depending on your soil’s needs, but typically, these are the amounts of limestone to use for different soil types:
- Sandy soils: 2 pounds per 100 sq. ft.
- Loamy soils: 3 ½ pounds per 100 sq. ft.
- Clay soils: 5 pounds per 100 sq. ft.
Be careful not to use too much, as lime can have adverse effects, like burning the plants.
You can also use wood ashes. This can raise the pH quickly but does not have as long-lasting effects. You will want to use ¼ inch of wood ash on the soil surface, then follow steps 3 and 4 below.
Be careful to not use ashes from chemically treated wood, and ensure that the ashes are dry. There are certain plants you will want to avoid using ashes on as well – like blueberries and azaleas, which love acidic soil. And try to avoid the ashes coming into contact with germinating seeds.
You can use baking soda, too. This is a cost-effective method that is quick and easy to do. Baking soda also does not last as long as lime (similar to the ashes) but can produce results in just a few days. Baking soda is fairly gentle on both the soil and the plants, so you won’t have to worry about harming your plants.
Mix a tablespoon of baking soda into a gallon of water. (You can use this ratio to increase or decrease the amount you need, based on the size of your garden.) Be careful not to add too much baking soda or use too much of this mixture in your garden, as it could create an imbalance. You can do this every few months as needed to maintain the optimum soil pH.
3. Mix the amendment of choice into the soil.
Once you have chosen an amendment and measured it out according to your needs, you will need to mix it into the soil thoroughly. You can do this with a rake, a shovel, a tiller, etc. Ensure the amendment is well mixed into the top 6 inches or so of the soil, so that it can really make the changes you are hoping to see in the pH.
4. Water the area well.
You will need to water the area very well, ensuring that it can reach a depth of at least 6 inches. This helps to activate the amendment so it can begin its work. You will want to water the soil regularly, but avoid overwatering as that can have adverse effects like leeching minerals and nutrients out of the soil.
5. Test the pH again after a few months.
Every few months, you will want to retest the soil to check on the status of the pH. This can help you learn if you used the correct amounts, and if it is still working (as different amendments can last different lengths of time).
Limestone takes longer to break down, so it will last longer than baking soda or wood ashes, but also may take longer to see the effects of the pH being raised. You may need to apply your amendment(s) again. If you do need to apply another round of limestone, you can do so in the fall. The other amendments can be done when/as needed in spring or fall.
pH levels can be affected by rainfall, fertilizer, and other changes in your yard’s conditions, so regular testing can help you catch pH problems before they cause issues for your plants