So many kinds of soil amendments are available claiming to improve your garden that it can be hard to know what is worth the investment. Are soil amendments really worth it, or is it okay to skip them in your garden this year?
Soil amendment is worth addressing specific problems in your garden, which can be identified through soil testing. Soil amendments can help correct soil pH, increase nutrient content, and improve soil texture. However, using soil amendments when they are not needed can cause problems.
This article will discuss what tests you need to perform on your soil before adding amendments and how to take and test soil samples.
Why Do You Need Soil Amendments?
The best way to know if soil amendment is needed in your garden is to perform soil testing. Adding soil amendment without a clear idea of your soil’s deficiencies can cause your soil pH to become out of balance and lead to nutrient toxicity.
If your soil tests indicate a need for supplementation in one area, you still need to look at the entire picture of your soil. To select the best amendment material, you must consider pH, nutrient levels, and soil texture.
If your soil amendments cause as many problems as they solve, they are not worth it. So do your research to get the maximum benefit.
Here are some reasons you might need to apply soil amendments to your garden:
Soil Amendments Can Adjust pH
Soil amendments can help stabilize pH levels in your soil. However, adding the wrong materials to your soil can disrupt a healthy pH. That is why testing pH levels before you amend soil is so important.
A neutral pH level is 7. Some plants require specific pH levels. For example, lavenders thrive in alkaline soil with pH levels up to 8.0. On the other hand, hydrangeas and blueberry bushes prefer more acidic soil.
That said, you need to select a soil amendment that addresses your plant’s needs. However, it can sometimes be impractical.
For instance, suppose you live in an area with naturally alkaline soil, but you’re trying to grow acid-loving plants. In that case, making your soil more alkaline can take a long time and cost so much money.
On the other hand, small changes in soil pH (up to 0.5) can be achieved through soil amendments.
Soil Amendments Can Correct Nutrient Deficiencies
There are 16 primary nutrients in soil that are necessary for plant growth. Each nutrient provides plants with unique support.
The essential 16 nutrients are:
While adding soil amendments that are high in nutrients may seem good, you have to be careful not to overload your soil with nutrients. Too many nutrients can lead to nutrient toxicity.
Remember: too much of a good thing can be a bad thing. That’s especially true for gardening. Some nutrients in excess can also alter the soil pH significantly, preventing plants from absorbing other nutrients they need and resulting in plant death.
Adding soil amendments that contain nutrients should be done carefully in response to low levels found through soil nutrient testing.
Soil Amendments Can Improve the Soil Texture
One of the benefits of soil amendments is that they can help improve the texture of your soil. While identifying your soil texture is not as precise as nutrient testing, having a general idea of your soil’s texture is crucial before picking up any soil amendment.
The texture of your soil is determined by its makeup of silt, sand, and clay, while the ideal texture is an even mix of the three. You can learn more about it from my other article: The Ideal Soil Texture for Planting Explained
The texture of your soil is so important because it can greatly impact its water retention and drainage capacities. When planned carefully, soil amendments can change your soil’s texture to better address your plants’ needs.
However, when used incorrectly, soil amendments can negatively affect how well or how poorly your soil can hold or drain water. It’s worth noting that plants have varying requirements regarding water retention and drainage.
Types of Soil Amendments
The problems identified in your soil testing will determine which soil amendments will benefit your garden.
Soil Amendments That Raise pH
To make your soil more basic, you will need to raise the pH of your soil. Here are some soil amendments that will help do so:
- Ashes: Ashes from wood (this is not to be confused with biochar, which are the ashes of plant material) raise pH and add calcium and potassium, two nutrients that have low levels in acidic soil. Ashes take some time to alter soil pH, so you should add them to your soil in the fall or winter to help improve your soil for the next spring.
- Lime: Lime contains calcium and magnesium, which also are low in acidic soil. Lime takes the same amount of time as ashes to change the pH of your soil.
To choose between the two, look at the magnesium and potassium levels from your nutrient testing and determine which needs more help. Soil amendments are worth it if you use the ones that can present the most benefits to your plants.
Soil Amendments That Lower pH
Lowering the pH of your soil makes it more acidic. Soil amendments that do this include:
- Peat Moss: Peat moss has very high water retention, so it’s not the best choice for clay soil. However, it does not have any nutrients, so it is a good choice to address pH specifically.
- Sulfur: A study conducted at the University of Florida found that water-dispersable sulfur was far more effective at lowering soil pH than the granular type. The water-dispersable sulfur significantly changed the soil pH within eight weeks of application.
Soil Amendments That Provide Nutrients
Compost and vermicompost are high in essential nutrients and are the best options for soil with several nutrient deficiencies. It is important to add these amendments slowly. They are very nutrient-dense, so it’s easy to overload the soil and cause nutrient toxicity.
If you want to learn more about how to make vermicompost, you can check out this article: How To Make Vermicompost from Kitchen Waste
For specific nutrient concerns, you can add:
- Calcium– gypsum, wood ashes
- Magnesium– Epsom salt, limestone
- Nitrogen– manure
- Phosphorus– bone meal, rock phosphate
- Potassium– greensand, gypsum, wood ashes
- Sulfur– water-dispersable sulfur
Soil Amendments That Impact Texture
Poor soil texture results from the imbalance of sand, silt, and clay. However, instead of adding any of these materials to restore the balance, you should use soil amendments to address the resulting water retention and drainage problems.
Soils with high sand and silt content have good drainage but poor water retention. Soil amendments for these types of soils should focus on improving water retention to prevent plant dehydration. Some examples include:
- Coconut coir
- Peat moss
Soils with high clay content have good water retention but trouble with drainage. Adding amendments that help improve drainage will prevent excess water from pooling around your plant’s roots, which helps prevent root rot.
Soil amendments that increase water drainage include:
- Pea gravel
- Peat moss
- Coconut coir
How To Add Soil Amendments to Your Soil
The key to adding soil amendments to your soil is to go slowly. Adding a little amendment at a time and retesting the soil regularly will help you avoid overcorrecting your soil deficiencies.
Most soil amendments intended to improve soil texture should be mixed directly into your soil, down to the root depth.
You can also add soil amendments on top of the soil around the base of the plant. Although it will not have a large effect on soil texture, the nutrients can slowly travel down to the roots every time you water your plants.
Soil amendments can be a worthwhile investment if you have specific problems with your soil.
Concerns should be identified by soil testing that includes:
- Nutrient levels
- Soil texture
Adding unnecessary soil amendments can:
- Throw off the pH of your soil
- Cause nutrient toxicity
- Affect the water retention and drainage of your soil
You should select soil amendments that address the problem areas identified in your soil tests, making sure to consider all of the effects of the amendments.
Remember to introduce soil amendments to your garden slowly and repeat testing often until your levels are normalized.