Does Soil Acidity Affect Plant Growth?

Whether you’re a new gardener or you have a green thumb, you may have some gaps in your knowledge. That’s perfectly fine, as so many factors must come together to create the perfect conditions for your soil and plants. So you may wonder, does soil acidity affect plant growth?

Soil acidity affects plant growth, crop yield, nutrient absorption, and even flower color. Some plants struggle to absorb nutrients in overly basic or alkaline soil, while others experience stunted growth in overly acidic soil. Research the ideal soil conditions for each of your plants, then plan your garden accordingly for the best results.

You can reduce soil pH to make it more acidic using peat moss and elemental sulfur. If the soil is too acidic, you can apply bone meal or ground oyster shells to make it more basic. Follow along as we explore everything you must know about how soil acidity affects plant growth.

How Does Soil pH Affect Plant Growth?

Soil pH affects the availability of essential nutrients needed for plant growth. It regulates how soluble certain nutrients are in the soil. When a nutrient is more soluble, the plant can more easily absorb it in a healthy way. Poor solubility can stop plants from absorbing key nutrients, which can cause a deficiencies. Soil pH can even affect how susceptible plants are to certain diseases and how effective pesticides are.

A casual gardener most likely doesn’t think much about soil acidity, even though it’s always a factor. That said, you must carefully research your plants and find out what soil pH is best for them. This is especially true if you have a variety of plants, as treating them all the same may yield uneven results.

What Is The Ideal Soil pH For Most Vegetables?

The ideal soil pH for most vegetables is 6.0 to 6.5, but it varies. This ensures healthy nutrient solubility and helps protect crops from diseases. In this pH range, vegetables can typically absorb key nutrients, like potassium, phosphorus, nitrogen, calcium, and magnesium. It also ensures that micronutrients are available, but not overly soluble. When the acidity is off, micronutrients can become toxic, and harmful bacteria can thrive.

For example, copper can become toxic and harm your vegetables when it becomes too soluble. A 5.5 pH level or lower can make aluminum and manganese toxic, while a 7.5 pH level can make boron toxic. It’s important to understand how soil acidity affects some specific nutrients. That way, you can correct soil acidity to ensure your plants can absorb the most essential nutrients.

What Is A Good Soil pH For Flowers?

The ideal soil pH range is different for flowers than it is for vegetables. That’s because some flowers love acidic soil, while others thrive best in neutral pH soil. For example, zinnias and marigolds thrive in 6.0 to 7.5 pH soil, while azaleas thrive in 4.5 to 6.0 pH soil. Soil acidity can directly affect your flowers’ appearance and color, but many people don’t know that. That’s especially true for hydrangeas, which can turn pink in neutral soil or turn blue in acidic soil. This may seem strange, but that’s because soil acidity affects aluminum levels, which can affect flower color. Keep in mind that soil pH goes hand-in-hand with deficiencies and nutrient toxicity. Some plant nurseries provide information regarding ideal soil conditions, so you should pay attention when buying new plants. Today, you can easily go online and find out the perfect soil acidity for each of your flowers. Group plants based on their soil acidity and sunlight needs to yield the best results.

How Do You Test Soil pH?

The best way to test soil pH at home is to use a soil pH meter or test kit. You can buy pH meters and test kits online, but many plant nurseries sell them as well. Soil pH meters offer the quickest results, and you can easily insert one into the soil. Make sure the soil is moist, or else you won’t likely get an accurate reading. The key is to insert the probe between 4” and 6” deep into the soil.

Home test kits are also effective, but they work quite differently from pH meters. First, dig a few inches deep, remove some soil, and mix it with distilled water. Add the capsule that came with the test kit, shake it, and let it sit for the allotted time. The color it turns will reflect the pH range in the directions that came with the test kit.

How To Reduce Soil pH

If your soil is too basic or alkaline, you may need to reduce the pH to ensure healthy growth and nutrient absorption. You can do so using a few key methods, such as:

Add Peat Moss

The best way to reduce soil pH is to add acidic organic matter, like peat moss. This is the best option because it’s widely available and highly acidic. It has a pH level of 3.0 to 4.5, and releases hydrogen ions when it breaks down. It's also a great long-term option because it slowly breaks down over 2 to 3 years. You can find peat moss at many plant nurseries and home improvement stores.

Use Acidic Fertilizer

Many people use fertilizer to enrich their gardens and encourage healthy growth. However, you may not realize that fertilizer can directly affect soil acidity. You can reduce soil acidity by using an acidifying fertilizer that contains ammonium sulfate. Some people use acidifying fertilizer in conjunction with peat moss to expedite the process. This may be necessary if your soil is too basic (high pH), but be careful not to overdo it. Test the soil acidity with a rapid test kit or pH meter after fertilizing it.

Apply Elemental Sulfur

If all else fails, you can also lower soil acidity by applying elemental sulfur. This is an interesting fix, as the elemental sulfur itself won’t directly reduce soil pH. Instead, the bacteria in the soil will slowly turn the sulfur into sulfuric acid through oxidation. However, many ideal conditions must align for this process to work perfectly. For example, it won’t likely work if your soil is compacted, as the soil must breathe well.

Ideally, you should aerate your soil before treating it with elemental sulfur. It also works best when the soil is damp and warm, so spring is a great time to do it. Keep in mind that the process takes roughly 3 to 6 months to work. Be patient and start as early as possible for the best results.

How To Increase Soil pH

Overly acidic soil is just as bad as overly alkaline soil. You can increase soil pH in a few ways, including:

Add Ground Oyster Shells

Sometimes, only a small part of your garden or yard has overly acidic soil. In that case, you don’t want to spend a fortune on a ton of calcium carbonate or bone meal. Look no further than ground oyster shells if you want to increase soil pH as cheaply and easily as possible. This is a great option if only a small patch of your garden is overly acidic. Dig some soil up, crush some oyster shells, and mix the dust into the top 2” to 4” of soil. The ground oyster shells will slowly dissolve into the soil and water, and they’ll release carbonate.

Use Bone Meal

Bone meal is rich in calcium, which means you can use it to increase soil pH and correct excessive acidity. Keep in mind it can only increase soil pH if the level is below 7.0. You can raise soil pH by mixing bone meal with potting soil. Mix up to 2 tablespoons of bone meal into each gallon of soil in the affected area. Try not to over do it, as the alkalinity issue may be confined to a small area.

Apply Calcium Carbonate

Calcium carbonate, also known as agricultural lime, can easily correct overly acidic soil, since it neutralizes hydrogen ions, which offers quick results. Ideally, pulverize the calcium carbonate to ensure it’s fine enough to easily blend into the soil. Mix the soil into the first 6” to 8” of soil to ensure it absorbs well. However, it’s worth calling a landscaper if your entire lawn is overly acidic. That’s because you may need to use literal tons of calcium carbonate, and that takes a lot of time and effort.

Summing It Up

Soil acidity affects plant growth because it determines the availability of key nutrients, like nitrogen and phosphorus. Excessive acidity can stunt plant growth and lead to a poor crop yield, while overly basic or alkaline soil can cause nutrient deficiency. Test your soil with a rapid test kit or soil pH meter before treating it, so you know exactly what level it’s at.

Related Guides:

• How To Tell If Your Garden Soil Is Compacted
• Six Signs Of Soil Erosion