Fertilizers and amendments are both substances used to improve soil quality and support plant growth, but they serve different purposes. Since these words are often used interchangeably, let's take a quick look at what they really are.
Fertilizers are materials that provide essential nutrients to plants, such as nitrogen (N), phosphorus (P), and potassium (K), to promote healthy growth and increase productivity. They do not change the soil structure.
Amendments are substances that improve soil structure, texture, and fertility by adding organic matter or minerals, enhancing water retention, and balancing pH levels.
In the most basic of terms, fertilizer application directly effects plants while amendment application effects plants through the soil health.
As you start the process of amending your soil, you'll come across various products with a (X-X-X) on the their label. It may be 0-5-1, 10-10-10, or any combination of numbers. These numbers are the Macronutrients; Nitrogen (N), Phosphorus (P) and Potassium (K). These are the nutrients that plants use most. There are also possibly listed on the side label some micronutrients such as Calcium (Ca), Magnesium (Mg) and Sulphur (S). These are nutrients your plants need, but in smaller quantities.
It's important to know what quantities are already in your soil because it's very possible to create nutrient toxicity if you add amendments that aren't needed.
Now that you know what those letters mean and what they do, let's look at some ways to get them into your garden. Below is a chart of some of the most common amendments and what they do. However, this list is not exhaustive. There are many ways to amend your soil, both organically or by using synthetics. There is no one 'right' way, so please choose the path that makes the most sense for you.
If this seems like a lot of science. It is. The key thing to remember is that while fertilizers directly supply nutrients to plants, amendments indirectly improve soil conditions, leading to better plant health and productivity over time.
Many companies that sell amendments and fertilizers are great resources for additional information on application and timing. Local garden clubs and your extension agent are also a wealth of knowledge. We encourage you to use our information as a springboard into your own research to build the garden you've always wanted.