Like all plants, blueberry bushes have particular conditions in which they thrive, including a suitable climate, sufficient sunlight, water, and appropriate planting time. Soil acidity is also one of the specific requirements of blueberry bushes. But how acidic is too acidic?
Soil can be too acidic for blueberries. Soils with a pH lower than 4 are too acidic to grow blueberry bushes. Soil acidity determines which minerals are available in the soil and in what amounts. And at pH levels below 4, many nutrients become unavailable for blueberry bushes.
This article will discuss the proper acidity levels for blueberry bushes. We will also look at the steps for testing the pH of your soil and how to amend the soil to alter its pH. Let’s get started!
The Ideal Soil Acidity for Blueberries
Most plants thrive best at pH levels close to 7.0, which is neutral. Around this level, most nutrients in the soil are available to plant roots for absorption. And as the pH deviates farther away from neutral, the nutrients become less accessible.
The ideal pH of soil for blueberry bushes is 4.5 – 5.0, but they can survive in soil with levels as low as 4. The pH of soil affects the type of bacteria that will be present in it, which in turn determines which minerals will be available. Acidic soil is high in iron, magnesium, and phosphates, which are all critical for blueberry bushes.
What Happens if Blueberry Soil Is Too Acidic?
If your soil is too acidic, blueberry plants will not be able to survive. At or below the pH of 4.0, the levels of essential nutrients in the soil decline rapidly. Bacteria also die in overly acidic soil, resulting in a lack of nitrogen. Soil begins to lose a lot of nutrients at a pH of 5.0.
Therefore, there is a smaller range of appropriate pH before the levels of minerals are so low that they cannot support the blueberry plants.
When soil pH falls below 4, there is a deficiency of many nutrients, including:
- calcium
- phosphorus
- magnesium
- boron
- copper
- zinc
- potassium
- sulfur
- manganese
How To Test Soil Acidity
pH is easy enough to test at home. There are digital meters, single-use testing kits, and laboratories that offer pH testing. Whichever method you choose, you will need to take a good sample of your soil.
- Select locations for testing. For increased accuracy, you should always take multiple soil samples distributed around the entire area of your garden. If you are sampling a sloped area, taking samples from the highest and lowest points will give you an understanding of how runoff affects the pH of your soil.
- Dig a hole 2-3 inches (5-7.5cm) deep. Unlike more comprehensive tests, pH tests do not require a deep hole. The objective is to get down below the grass and other surface substrates.
- Remove any remaining debris. Even under the surface, there can be materials in the soil. Things like rocks, worms, and roots should all be removed to get the cleanest sample possible.
There are three ways to test your soil’s pH level, depending on your location and the availability of resources. They also have different levels of accuracy, so it helps to choose which one is convenient and reliable. Let’s check them out below:
Single-Use Test Kits
If you are using an at-home kit, you will need to collect ½-1 cup of dirt from the hole and place it in a bowl or container. As discussed, it helps to collect soil samples from different spots in your garden and label them accordingly.
Add enough distilled water slowly until you have thick mud. Note that the water must be distilled, or the pH of the water will make your reading inaccurate. Follow the instructions on your kit to insert the test strip and interpret the color results.
Digital Meters
If you use a digital meter, you do not have to extract a soil sample. Instead, add distilled water directly into the hole you dug and place the meter into the mud mixture. Be sure that the soil pH meter’s prong is clear of contaminants that can alter your readings.
Most meters take about a minute to measure the pH levels.
Laboratory Test
A laboratory test will give you the most accurate results. In addition to soil pH, you can also find out the nutrient levels and overall health or fertility of your garden soil. However, depending on your region, lab tests can be costly.
To send samples off to a laboratory, you will need clean bags. Generally, a sample of 1-2 tablespoons of dirt is sufficient, but make sure to check your lab’s instructions. You may want to keep samples from different locations separate for a larger garden.
Make sure to label your samples with as much detail as possible so you can interpret your results more easily.
Soil acidity will change over time, so you should test your soil pH monthly or quarterly. If you are trying to change the pH of your soil, you may want to test it more frequently while applying the amendments.
Note that you may need to take precautions if you’re testing your soil during the winter months. I’ve discussed what needs to be done in a complete guide on the topic: Can You Test Soil Quality in the Winter?
How To Make Soil More Acidic
There are lots of different ways to make your soil more acidic.
The amount of additive you need is determined by your pH at the beginning. The more you need to lower the pH of your soil, the more additive you will need. Additionally, clay is more resistant to changes in pH, so soil with more clay will require more supplementation.
It helps to remember that blueberries prefer sandy soil. However, some sand sources may contain limestone or similar materials that can increase the pH. That’s why it’s essential to have your soil tested before growing blueberries.
You can make the soil more acidic in various ways. Let’s look at them below:
- Elemental sulfur is one option for increasing the acidity of your soil. If you want to use elemental sulfur in your soil, you will need to plan ahead, as it can take several months to a year to reach its full effect.
- Apply sulfate fertilizers into the ground. Sulfates are compounds of sulfur and another element, typically aluminum or iron. While it is not as pure as elemental sulfur, it does work a little faster.
- Pour diluted vinegar into the soil. This is one of the fastest methods available. The vinegar must be diluted in water, two tablespoons for every gallon. You will need to apply it weekly to maintain the soil acidity.
- Use acidic coffee grounds. Remember that not all coffee grounds are acidic. Some coffee grounds have a pH of around 5, which can significantly lower soil pH. So you must test the pH of the grounds before use. You may need a large amount of acidic coffee grounds, but be careful that it doesn’t block air pockets in the soil because blueberry roots need adequate aeration.
- Peat moss is another option for acidifying soil. Peat moss has a pH of around 3, so you must be careful not to add too much, or your soil may become too acidic. If you have time before planting, add it slowly, testing along the way. You should need about 4 to 6 inches (10 to 15 cm) of peat moss in your soil. If you source your peat moss from garden stores, check the pH level as it may not be acidic enough.
- There are also fertilizers that can make your soil more acidic. Read the label carefully, as not all fertilizers are natural. However, there are plenty of chemical-free options available.
How To Make Soil Less Acidic
Making soil less acidic, or raising the pH level, can be done naturally with different soil amendments.
- Lime, or powdered limestone, works well because it is very finely ground. However, it takes a while to change the pH of the soil, so you should apply it a few months before you plan to plant your blueberry bushes.
- Compost has a neutral pH, so it can raise the levels in the soil. In addition to raising the pH, compost contains a wide variety of essential nutrients that can help restore the minerals that die off in acidic soil.
- The ash of wood is another soil additive that helps raise the pH levels. It is a great way to save money and repurpose your waste if you have a wood-burning firepit or fireplace.
Conclusion
The ideal soil acidity for blueberry bushes is between 4.5 and 5 pH. This level provides the plant with the essential nutrients and bacteria to thrive. If your soil is not in the acceptable pH range, there are many natural supplements you can add to raise or lower the pH.
To learn more about improving soil for blueberries, check out this article: How to Improve Soil for Blueberries: 6 Easy Methods
