how to make soil more acidic for blueberries

Blueberry plants can be as short as 1 foot tall or as high as 12 feet tall, but no matter how big they are, blueberries need the right conditions for growth. This includes full sun, well-draining soil, and the proper soil pH. So, do blueberry plants like acidic soil? Blueberry plants like acidic soil, and they grow best at a soil pH of 4.5 to 5.5. They can survive a soil pH as low as 4.0, but strongly acidic soil causes nutrient deficiencies. In clay soil, aim for a pH of 5.5, since clay soil that is too acidic will stick together and is hard to work with. Of course, if your soil pH is too high, there are some ways to acidify the soil, including sulfur, sulfates, and fertilizers. In this article, we’ll talk about ways to acidify soil and when you might use each one. We’ll also answer some common questions about soil amendments for blueberry plants. Let’s begin. Do Blueberry Plants Like Acidic Soil? Blueberry plants like acidic soil with a pH of 4.5 to 5.5. In clay soil, aim for a pH closer to 5.5, since clay soil that is too acidic sticks together and is difficult to work with. Blueberry plants prefer acidic soil with a pH of 4.5 to 5.5. Most garden vegetables prefer soil with a pH of 6.0 to 7.0. For this reason, it is a good idea to grow blueberries in a separate area with acidic soil. Once you have an area of your garden dedicated to acidic soil, you can add other acid-tolerant plants, such as: Azaleas (ideal soil pH of 5.0 to 5.5)Blackberries (ideal soil pH of 5.5 to 6.5)Potatoes (ideal soil pH of 5.3 to 6.0)Rhododendrons (ideal soil pH of 5.0 to 5.5)Sweet Potatoes (ideal soil pH of 5.5 to 6.8) Potato plants also prefer acidic soil, with a pH of 5.3 to 6.0. Although blueberry plants like a lower soil pH than most other plants, they can only tolerate so much acidity. Can Soil Be Too Acidic For Blueberries? It is possible for soil to be too acidic for blueberries. The Cooperative Extension suggests that blueberry plants can tolerate soil with a pH as low as 4.0. However, many plants will begin to suffer from nutrient deficiencies in such acidic soil. Blueberry plants can tolerate acidic soil, but a pH below 4.5 increases the chances of nutrient deficiencies. The reason is that a low soil pH reduces the availability of certain nutrients in soil. This means that a plant’s roots are not able to absorb those nutrients from soil that is too acidic. For example, the availability of nitrogen, calcium, and magnesium all drop off rapidly as soil pH approaches 4.0 (you can see this illustrated in this figure from Research Gate). Soil that is too acidic can cause a nutrient deficiency in plants - even when there is plenty of a given nutrient in the soil! How Do I Know If My Soil Is Acidic Enough For Blueberries? The best way to tell if your soil is acidic enough for blueberries is to do a soil test. You have a few different options for this: Traditional Soil Test Kit – this type of soil test uses tablets to test soil pH along with nitrogen, phosphorus, and potassium levels. A.M. Leonard has a soil test kit available.Digital Soil Tester – this type of soil test uses a metal probe that goes into the soil. An electronic screen can tell you the soil pH level, along with nitrogen, phosphorus, and potassium levels. They are more expensive, but faster than a traditional soil test kit. A.M. Leonard has a digital soil tester available.Lab Soil Test – you also have the option to send a soil sample to a private lab or a local agricultural extension office for analysis. In addition to soil pH and nutrient levels, they can give you detailed recommendations based on the specific plants you are growing (just make sure to indicate what you are growing on the forms you fill when you order the test). You can find a list of University Extensions (by state) on this page from the USDA. You can learn more about how to do a soil test in my article here. You can also learn about what a soil test tells you in this article. There are three possible cases in the aftermath of a soil test for growing blueberries: Soil pH below 4.5: this is rare, but blueberry plants can still survive in soil with a pH of 4.0 to 4.5. However, soil that is so acidic may cause nutrient deficiencies, so you might want to adjust the soil pH slightly upward. You can use lime or other soil additives to do this – and you can learn more about how to raise soil pH in my article here.Soil pH between 4.5 and 5.5: if your soil pH is in this range, it should be fine for growing blueberries - you don’t need to make any adjustments to the soil pH!Soil pH above 5.5: if your soil pH is in this range, it might not be acidic enough for growing blueberries. Check the instructions below for ways to make soil more acidic for blueberries. SoilpHNotesActionLessThan4.0This soil is too acidic for blueberries. Nutrient deficiencies are more likely in such acidic soil.Add lime to raise soil pH.4.0to 4.5Blueberries can survive in soil this acidic, but it may cause nutrient deficiencies.Add limeto raisesoil pH.4.5 to 5.5This is the ideal range for blueberries.No action needed.Over5.5This soil is not acidic enough for blueberry plants.Add sulfur to lower pH.This table gives a summary of soil pH ranges for blueberry plants and what actions to take in each case. How To Make Soil More Acidic For Blueberries If a soil test reveals that your soil is not acidic enough for blueberry plants, don’t worry. There are plenty of ways to lower your soil pH so that blueberries will thrive, including: Elemental SulfurAmmonia Based FertilizersSulfates Let’s start by taking a look at elemental sulfur, which is a commonly used soil acidifier. Elemental Sulfur Elemental sulfur is just pure sulfur. This makes things simple, since you know exactly what you are adding to your soil. Elemental sulfur will lower soil pH over the course of a year or more. According to the Michigan State University Extension, soil bacteria will work to change sulfur to sulfuric acid (H2SO4), which lowers soil pH. They suggest that spring is the best time to add sulfur to garden soil, since the bacteria that convert sulfur to sulfuric acid will be more active. They also warn that the soil should not be soaked, or else anaerobic bacteria will turn sulfur into hydrogen sulfide (which kills roots). Elemental sulfur is not a quick fix – rather, it will slowly lower soil pH over time. In fact, the Michigan State University Extension suggests that you add sulfur at least one year before planting. Of course, the amount of sulfur you need to use depends on three things: Soil Texture – you will need less sulfur to acidify sandy soil than clay soil. The reason is that clay and organic matter act as a pH buffer, preventing pH changes.Starting Soil pH – the higher the soil pH, the more sulfur you will have to add to achieve the desired soil pH.Desired Soil pH – it will take more sulfur to change soil to a very low soil pH. Clay soil is heavy with fine particles, and it will take more sulfur to acidify such soil. The University of Michigan has a table here, but it is in pounds of sulfur per acre. I have converted the table below to show ounces of sulfur per 100 square feet. SoilpHSandLoamClay5.06.419.529.45.512.937.858.86.019.556.684.56.524.274.2111.37.030.994.0140.7Ounces of sulfur per 100 square feet needed to lower soil pH to 4.5. Ammonia Based Fertilizers Ammonia based fertilizers (ammonium sulfate) have the appearance of white pellets. Ammonium sulfate will lower soil pH and add nutrients at the same time, and it will lower pH faster than elemental sulfur. Ammonium sulfate will acidify soil and add nitrogen needed for growth. However, you run the risk of burning your blueberry plants due to the rapid change in pH and high levels of nitrogen & salts. (You can learn more about over fertilizing your plants (and how to avoid it) in my article here.) Sulfates Sulfates (such as iron sulfate or aluminum sulfate) have the appearance of crystals. They work faster than elemental sulfur to acidify soil. However, you will need to use a lot more sulfate than elemental sulfur to get the same change in soil pH. In fact, the Michigan State University suggests that you will need 8 times as much iron sulfate as sulfur to get the same effect! In addition, too much sulfate can lead to excessive metals in your soil. For example, iron toxicity can occur in acidic soil after using iron sulfate. How Do You Acidify Soil Quickly? To acidify soil quickly, use ammonia based fertilizers or sulfates. Both of these work faster than elemental sulfur to lower soil pH. Using ammonia based fertilizers will acidify soil faster than sulfur, but it can lead to excessive nitrogen if you add too much. High nitrogen levels can prevent flowering of blueberry plants, which will reduce yield. Using sulfates (such as iron sulfate) will also work faster than sulfur. However, this method is much more expensive. If you can wait, use sulfur, since it is more cost effective and safer for your soil & plants. Are Coffee Grounds Good For Blueberries? I think it would be fine to add coffee grounds to a compost pile, let them decompose with the rest of the material, and use the compost around your blueberry plants. Coffee grounds are good for compost, but they will not change soil pH noticeably. Coffee grounds are slightly acidic to mildly acidic, but they will not acidify soil. Is Epsom Salt Good For Blueberries? Epsom salt is good for blueberries if they need magnesium (or sulfur), but it will not change the soil pH noticeably. However, as with most other soil additives, it is possible to add too much Epsom salt to your garden. Epsom salt (magnesium sulfate) will provide magnesium and sulfur for plants, but it will not change pH much (if at all). According to the University of Minnesota Extension, adding too much Epsom salt can interfere with calcium uptake by roots (due to excessive magnesium). Your best bet is to do a soil test first. Then, add a little bit of Epsom salt if there is a lack of magnesium. Conclusion Now you know what kind of soil blueberry plants like and how to make it more acidic. Looking for garden inspiration? You can learn about 25 blueberry varieties to try planting here. You can learn more about which fertilizers are acidic in my article here. You might also want to check out my article on vegetables for acidic soil. I hope you found this article helpful. If so, please share it with someone who can use the information. If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy! ~Jonathon