3 Reasons Why Acidic Soil May Be Great For Your Trees

Small tree growing in garden with morning light

Did you know certain plants love acidic soil, while others despise it? Acidic soil can be great for your treess, especially if you live in areas that have loamy soil. On the other hand, it could be an issue for plants that don’t tolerate acidic soils well.

Acidic soil can be great for acid-loving plants. Soil pH determines the nutrient uptake and growth of your tree or plant. Acidic soil gives them access to a range of nutrients that aren’t necessarily available in lower soil pHs. Rainwater plays a heavy role in how acidic soil becomes.

Soil pH can be tested to determine if your soil is acidic, alkaline, or neutral. So, if you want to find out if acidic soil is good for your tree, keep on reading!

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Is Acidic Soil Really Good For Trees?

So, when you hear acidic, you’re probably thinking, “Well, isn’t acidic soil bad for trees?” And, while that’s the case for some trees, it’s not the case for all, which is kind of counterintuitive. 

Some plants, those that are considered ‘acid-loving’ need more of the nutrients that are readily available in acidic soils. This includes evergreens, hydrangeas, rhododendrons, and even blueberries. 

According to SUNY Environmental College of Science and Forestry, a lot of nutrients are more readily dissolved in acidic soils rather than in neutral and alkaline soils, which is why certain trees and plants do better in it. 

Some trees prefer a soil pH of 6.6-7.3, which is considered a neutral pH. Acidic soils are defined as soils that have a pH of less than 6.6, neutral soils have a pH range of 6.6-7.3, and anything above that is considered alkaline. 

Let’s dive into the reasons why acidic soil is great for your trees!

1. Acidity Helps Your Tree Absorb Nutrients

Woman hand plants a tree on soil

Trees need specific nutrients and minerals to complete photosynthesis, grow, and carry out their natural processes. These nutrients are separated into three different categories: Primary, secondary, and micro-nutrients.

Primary nutrients, called macronutrients are nutrients that plants require the most and in the largest quantities. Primary nutrients include carbon, hydrogen, oxygen, phosphorus, and potassium. These nutrients are responsible for the major plant functions of plant structure, respiration, water retention, cell formation, and energy production. 

Secondary nutrients include calcium, magnesium, and sulfur, which are needed in moderate amounts. Certain plan functions of secondary nutrients are enzyme activities, metabolism, protein, and amino acid formation. 

Micro-nutrients for trees are boron, chlorine, copper, iron, manganese, molybdenum, and zinc. These nutrients are needed in very small amounts in comparison to primary and secondary nutrients. These nutrients are mainly responsible for enzyme activity.

If you have an oak tree, check out our guide on the best oak tree fertilizers so they get the right nutrients!

For plants to effectively take up nutrients, they have to be in specific forms, and water-soluble otherwise they cannot be used by the tree or plant.  

Did you know that soils with lower pH levels have certain nutrients that are more readily available? 

Well, it’s true. Plants can easily uptake nutrients such as iron, aluminum, and manganese. The same is true for more alkaline soils, the only difference being different nutrients that are available.

At certain pH levels, some nutrients are not in available forms for plants to uptake. This is determined by the microorganisms and microbes present in the soil, which ranges from different soil types.

If you have a spruce tree, I highly recommend checking out our guide on the best spruce tree fertilizers here to get the pH right!

2. Your Tree Has Access To Nutrients Only Found In Acidic Soils

Big tree root

Soil pH refers to the concentration of hydrogen ions within the soil. So in soils with a low pH, there is a greater amount of hydrogen ions than in soils with a high pH. 

Because of the high concentration of hydrogen ions in acidic soils, this gives trees access to the nutrients they need. 

Like the primary, secondary, and micro-nutrients we mentioned above, such as zinc, iron, manganese, aluminum, copper, and boron, which are all found in greater amounts in acidic soil than in neutral or alkaline soils. 

Even certain nutrients such as calcium, magnesium, sulfur, and nitrogen are moderately present throughout acidic and alkaline soils. 

Species like green ash, bald cypress, river birch, cottonwood, dogwood, magnolia, longleaf pine, slash pine, and sweetgum are just a few tree species that tolerate acidic to neutral or alkaline soils. 

3. Soil pH Influences Plant Growth And Beneficial Bacteria

Close up of earth worms on the ground

Soil pH can affect the beneficial bacteria that live in the soil. These microorganisms help decompose organic matter and influence the growth of plants, including your tree.

However, certain soils that are highly acidic limit the amount of decomposition from bacteria, resulting in less organic matter broken down.

This can become an issue. It can limit the number of nutrients that can be taken up by the tree, such as nitrogen. 

Depending on the type of soil, certain nutrients are not in available forms for plants to uptake and readily use. Microorganisms and microbes present in the soil are responsible for breaking them down to enable plants to take them up effectively. But, this ranges from different soil types.

According to Washington State University Extension, most of the nutrient cycles within the soil are directly controlled by the microbes within the soil.

This helps trees and plants absorb nutrients through organic matter decomposition, and nitrogen-fixing. Plants would not be able to as effectively acquire nutrients from the soil without the help of microorganisms.

If you have maple trees, take a look at our piece on the best maple tree fertilizers here!

How Soil Becomes Acidic (And What Nutrients Are In It)

Background with a path of olive trees on a cultivated field

As we touched on above, acidic soil has a soil pH of less than 6.6, which contains those certain nutrients that are lacking in abundance in neutral and alkaline soils. This includes primary, secondary, and micro-nutrients like Zinc, Iron, Manganese, Aluminum, Copper, and Boron. 

Other nutrients, such as Calcium, Magnesium, Sulfur, and Nitrogen are moderately present across the board in acidic to alkaline soils. 

According to SUNY Environmental College of Science and Forestry, the soil becomes acidic as a result of things that happen in the environment. 

Leaching of nutrients from soil can be caused by: rainwater, the formation of weak organic acids, and the formation of strong organic and inorganic acids. 

Rainwater can leach or drain away minerals like calcium, magnesium, potassium, and sodium. 

The formation of weak organic acids can also be a result of the combination of carbon dioxide from decomposition and root respiration dissolving in water. 

Lastly, the formation of strong organic and inorganic acids is a result of decaying organic matter and oxidation.

Any areas that have higher rainfall are going to tend to have more acidic soils. This happens due to the ionization that happens when water combines with carbon dioxide, thus releasing hydrogen and bicarbonate.

These hydrogen ions (hydrogen and bicarbonate) then replace the calcium ions (that were already in the soil), resulting in the acidity of the soil.

From there, a water-soluble ion of calcium and bicarbonate bonds together and is formed and drained from the soil. This process is much more complicated, but this is just a quick synopsis of what happens. 

Soil pH is affected by things such as the parent soil material, rainfall, organic matter, or fertilizers. Nitrogen fertilizers can also increase soil acidity. So this means that if nitrogen fertilizer is applied at a greater rate, the soil is going to become more and more acidic.

Changing The Soil pH

You can change the soil pH by adding materials or additives to the soil. This includes things like limestone, and wood ashes.

Because of the nutrients present within limestone and wood ashes, you can raise soil pH in the case that you want your soil to be less acidic!

Before you guess whether your soil is acidic or alkaline, the best thing to do is test it! The Luxekem Soil pH Meter is a great choice. It has four functions including soil moisture, pH, temperature, and sunlight intensity, so you’ll be able to test just about everything at once.

Above, we mentioned the different primary, secondary, and micro-nutrients that are present in acidic soil. Adding a wood ash amendment to your soil can increase the pH but in slow increments.

Wood ash is high in potassium and calcium and can be spread into a thin layer during the winter and turned in in the springtime. 

Using a limestone application can also increase the pH of the soil. Limestone is primarily composed of calcium carbonate and adds calcium into the soil, neutralizing acidic soil.

You can use things like calcification limestone, dolomitic limestone, hydrated lime, ground oyster shells, pelletized lime, and fluid lime. 

After you test the pH of your soil, if you decide you want to change it, you can add an amendment like Garden Lime 6.75 lbs. The Epsoma brand makes amazing products, plus it’s organic. It also comes in pellets so it’s easier to apply and adjust the pH of your acidic soil.

You can learn more about the specific pH’s that trees like here!

Acidic Soil Can Contribute To More Storm Damage And Soil Toxicity

Forest in early autumn before storm with a dramatic cloudy sky

Believe me, when I learned of this, I wondered how it could be true for quite a bit.

A study done by the Swiss Federal Institute for Forest, Snow, and Landscape Research, assessed the effects of soil properties, specifically, the acidity of the soil. 

What they found was that soil pH had the most significant impact on storm-damaged plots and that it should be considered a risk factor in the susceptibility of forests to damage from storms. 

They suggest that an increase in deciduous trees would reduce the amount of damage and susceptibility that forests have to storms. 

So, while acidic soil may be good for some trees, and some landscapes, in others, it drives damage from natural disturbances. 

Soil pH can also limit the growth of certain trees and plants and make it impossible for them to live in a certain location.

Too low of a pH can also cause toxicity to plants. This means that certain nutrients are only available at toxic levels, like aluminum and manganese, or nutrients won’t be able to be absorbed, at all.  

This results in yellowing leaves, stunted plant growth, and development, and can even cause the plant to end all together.

If you weren’t sold on the pH meter above, or you just want something easier to read, you can try the Garden Tutor Soil pH Test Kit (3.5-9 Range). These soil pH test strips give you results in just 60 seconds so you can optimize your soil pH. 

That’s A Wrap!

While acidic soil can be great for acid-loving plants, for other plants it can be detrimental. 

Soil pH determines the nutrient uptake and growth of your tree or plant. Acidic soil gives trees and plants access to a range of nutrients that they may not get from other soil types. 

If your soil is too acidic for your plant or tree you can use different soil amendments like limestone to increase the pH of your soil.

On the other hand, a soil pH that is too low can cause toxicity or plant poisoning, where certain nutrients are only available at toxic levels. 

Lastly, soil pH has a significant effect on storm damage to forest plots and makes forests more susceptible to storm damage.

Thanks for learning with us about why acidic soil is good for your tree!

References

Bagayoko, M., S. Alvey, G. Neumann, and Andreas Bürkert. “Root-induced increases in soil pH and nutrient availability to field-grown cereals and legumes on acid sandy soils of Sudano-Sahelian West Africa.” Plant and Soil 225, no. 1 (2000): 117-127.

Mayer, P., Brang, P., Dobbertin, M., Hallenbarter, D., Renaud, J. P., Walthert, L., & Zimmermann, S. (2005). Forest storm damage is more frequent on acidic soils. Annals of Forest Science, 62(4), 303-311.

McCauley, A., Jones, C., & Jacobsen, J. (2009). Soil pH and organic matter. Nutrient management module, 8(2), 1-12.

Ohno, Tsutomu, and M. Susan Erich. “Effect of wood ash application on soil pH and soil test nutrient levels.” Agriculture, Ecosystems & Environment 32, no. 3-4 (1990): 223-239.

Stark, Sari, Minna K. Männistö, and Anu Eskelinen. “Nutrient availability and pH jointly constrain microbial extracellular enzyme activities in nutrient-poor tundra soils.” Plant and Soil 383, no. 1 (2014): 373-385.

Zhalnina, Kateryna, Raquel Dias, Patricia Dörr de Quadros, Austin Davis-Richardson, Flavio AO Camargo, Ian M. Clark, Steve P. McGrath, Penny R. Hirsch, and Eric W. Triplett. “Soil pH determines microbial diversity and composition in the park grass experiment.” Microbial ecology 69, no. 2 (2015): 395-406.

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