Soil PH - How Does It Affect Your Plants?

Diving into the vast work of Soil pH can be intimidating. There's a lot of information and the science of balancing the correct pH for a plant takes time and research. To make it easier, I'm going to break down some of the basic compounds that can be used to help grow beautiful and healthy plants.

The pH Scale

pH doesn't have a standard definition but is instead a long algorithm that measures how acidic a substance is. Why do we care about pH when it comes to plants and soils? Because finding the correct pH balance has a direct impact on how well plants live. Plants pull the nutrients needed to grow, flower, and reproduce directly from the soil they are planted in.

The ""Goldilocks Zone"" is considered the perfect zone on the pH scale for plants to absorb nutrients. For most plants 6.5 on the scale hits that goldilocks zone and is the aim when adjusting pH as this allows for the best uptake of nutrients across the board (explained in the Nutrient section). It can be difficult to land right at 6.5 on the pH scale, so aim for 5.4 - 6.5 for optimal coverage of most plants.The first thing I think about when it comes to pH is nutrient uptake. Ultimately what you're trying to do is create a balance of nutrients so plants can pull exactly what they need to thrive. The goldilocks zone being at 6.5 on the pH scale is where you get the best available for your macro and micronutrients.Certain flowers will actually have different phenotypic expressions under certain pH conditions. For example hydrangeas at a lower pH will cause the blooms to turn blue, while a higher pH will make them pink.Other plants like blueberries need a lower pH to be productive. Rhododendron also enjoys a lower pH since it's in the evergreen family.With products like lime and sulfur, you can raise and lower the ph of your soil to help with nutrient uptake, in addition to manipulating the pH.

pH Differences

Knowing about soil and the pH scale is good and all, but how does this effect plants? Why do we care about balancing soils? Because having pH too high or too low can change a plant.Certain flowers will actually have different phenotypic expressions (appearances) under certain pH conditions. For example hydrangeas at a lower pH will cause the blooms to turn blue, while a higher pH will make them pink. Other plants like blueberries need a lower pH to be productive. Rhododendron also enjoys a lower pH since it's in the evergreen family.Negative consequences can also be seen with different pH levels. Chlorosis is the yellowing of leaf tissue between inner veins and can be caused by high pH and nutrient deficiencies. Marginal Necrosis (browning of lead tips) can be an indication of pH being too low.

Further, high pH can drastically limit how much iron and boron are absorbed (leading to the Chlorosis), and too low will over absorb nutrients like potassium and sulfur.Figuring out how to balance pH in plant soil is a great way to set plants up for success.

Nutrients

With products like lime and sulfur, you can raise and lower the ph of your soil to help with nutrient uptake, in addition to manipulating the pH. Beyond pH levels, these additives can actually add direct nutrients to the soil. Lime will add calcium and magnesium while sulfur adds sulfur.The scale below shows at what pH level each individual nutrient is most effective. By balancing pH to 6.5 on the scale each nutrient has a better chance of being absorbed by the plant, which makes for happier plants.

The most common additives to soil are lime, gypsum, and acidifier. These adjust pH balances when added to bases.

Testing

Of course, the only way to know the pH of soil is to test. Products and kits to accomplish this can be purchased online or from local nurseries.The PourThru method is a way to pull water through soil to test the pH balance and make decisions about nutrient treatment. For more information, check out this resource: The Pour-Through Extraction Procedure: A Nutrient Management Tool for Nursery Crops.

Making Your Own Substrate

All this information builds to allow you to make your own substrate mixture. You can test soils you're currently using to adjust levels, or you can build from scratch.All substrates start with dirt and are then adjusted with basics such as peat moss and vermiculite. When adding things to soil changes in pH can happen. Peat has a really low pH at around 4.5, so you would need to add lime to raise the PH in order to create a good substrate for growing plants.This is where gypsum comes in. Since gypsum is calcium sulfate, the pH balance is neutral (not acidic, and not alkaline). When working with substrates like coco coir, which has a ph of 6.2 to 6.7, you wouldn't want to deviate from the goldilocks zone of perfect pH. Adding gypsum along with calcium and sulfur allows the balance to continue. [button-green url="https://www.joshsfrogs.com/sprigandstone/soils-and-such/ingredients-for-soil-mixes.html" target="_blank" position="center"]Purchase Soil Conditioners[/button-green]

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