Compost vs. Fertilizer – What’s The Difference?

Compost vs. Fertilizer - What’s The Difference?Spring is nearly here which means that it's time to get many plants into the ground. Will you be adding compost or fertilizer to your plants? While it seems like a simple question, there's actually a lot more to it. What kind of nutrients do your plants need, if anything? Should you add fertilizer or compost, or both? And what's the difference? We did a lot of research and found the answer for you!

Compost provides nutrients to the soil while fertilizer feeds the plants themselves. Compost is broken down organic material that often comes from a compost pile. Fertilizer, on the other hand, is an additive used the enhance plant growth. Compost is also generally an organic material, while fertilizer is most often synthetic.

Let’s take a closer look at the differences between compost and fertilizer and determine which one is best for you and your plants.

Is Compost Better Than Fertilizer?

There is no clear cut “best” between compost and fertilizer. It all depends on your situation and the needs of your plants and soil. Both fertilizer and compost have a variety of benefits and disadvantages.

Benefits of fertilizer:

  • Fast fix to soil deficiencies
  • Can be catered to your soil’s specific needs
  • Is readily available at many different stores

Disadvantages of fertilizer:

  • Does not benefit the soil itself
  • Overuse may cause damage to the plant and soil
  • Synthetic fertilizers are not good for the environment

Fertilizer is a good option if you are looking for a fast fix to a specific problem such as nitrogen deficiency, or if you know that a certain plant needs a specific nutrient. For example, you could add nitrogen-rich fertilizer to spinach because it will enhance the foliage. However, the same may not be the case for tomatoes, as you want more fruit than foliage.

Benefits of compost:

  • Increases water retention and weed control
  • Protects against erosion
  • Enriches the soil in the long-term

Disadvantages of compost:

  • Requires input or a source
  • Dangerous if not properly processed
  • Dirty and often has an odor

In general, compost is a good and safe option, as too much fertilizer can damage or kill plants and hurt the surrounding environment.

Compost can also be dangerous but in a different way. If compost is not properly treated, turned or prepared, diseases in the compost may damage the plants. Be sure to get your compost from a trusted source. One of the best places to get compost is your own home. A compost pile or tumbler is a great way to reduce waste and benefit your plants.

Read more: How Much Does a Compost Tumbler Cost?

What Is The Difference Between Soil And Compost?

Horse manure compost and worms in hands

Soil, or topsoil, is the top layer of the earth that is a mixture of organic material, clay, and rock. If you buy topsoil, it is important to know that there are three grades of soil. The three grades are premium, general or economy. With the lower grades, there is an increased chance of disease or weeds being in the soil. Lower-grade soil also typically has fewer nutrients.

In contrast, pure compost is made 100% of organic material. Compost may be made out of organic materials ranging from manure to food scraps, and it is most often used to “feed” the soil and the plants living in it. Compost is best used as a nutrient additive or feed for your soil.

Can you use compost instead of soil?

In theory, yes, you can use compost instead of soil. However, it may not be a good idea to do so, as compost may have a variety of PH and NPK values which may not be beneficial to your plants. Compost is meant as a soil feed and amendment, not as a growing medium. Using it as a growing medium in large amounts is also not sustainable, as it takes time and energy to produce high-quality compost.

It is best to use soil as the base and use compost as a cover. Not only will that help the nutrition levels but will also prevent water runoff and stunt weed growth.

If you are concerned about the PH or NPK levels of your soil or compost, consider having a soil test done. They can tell you a lot about your soil and what kind of plants will do well. You can buy a soil testing kit or, in the US, soil tests can be conducted by your local extension office. Many people recommend having a soil test done every year or so, which is a good idea especially if you add compost to your soil.

Can You Combine Compost And Fertilizer?

A man in gloves holding a shovel with fertilizer

Yes, you can combine compost and fertilizer! In fact, it is generally a good idea to use compost and fertilizer in combination with one and other or add fertilizer to your compost.

Compost and fertilizer perform different and complementary jobs. By adding both to your plants, you can help the life of your plants and the soils they live in.

It is important to realize you need to be careful about how much fertilizer and compost you are using. It is very easy to use too much fertilizer, but you can also use too much compost if you are not careful. Having too much of both can be especially damaging to the soil and the microbiome.

For example, if you add a nitrogen-rich fertilizer and a nitrogen-rich compost your plants may grow an excess of foliage and produce less fruit. The goal is to have a well-balanced soil or soil with nutrients the plants need.

Compost vs. Fertilizer Experiments 

This article takes a look at a large scale experiment of chemical fertilizers versus common organic composts such as chicken and cow manure. It takes a detailed look at the NPK (nitrogen, phosphorus, and potassium) levels. The study found that it is important not to add too much fertilizer in order to prevent nitrogen leaching. Take a look at the study for more detailed results.

" data-lasso-id="5765">This YouTube series explores the effects of liquid fertilizer feed on tomato plants versus compost. They found that the plants with compost had less blight and were generally more resistant to disease. However, the fertilized plants grew more and had additional foliage. The video also addresses adding too much of one particular nutrient, as a few of the plants grew curly leaves due to an excess of nitrogen, which is a common problem with fertilizer use.

Last but not least, check out this small-scale experiment. The experiment tested to see whether compost or fertilizer helped beans grow better. They found that organic compost worked better, but they were using guinea pig manure, which is different from many other quality composts.


In conclusion, compost and fertilizer are different in many ways, from composition to use. Compost is made mostly of organic material and slowly adds nutrients to the soil. Fertilizer is typically synthetic and is focused on providing fast nutrients to plants. While both compost and fertilizer both have their uses, compost is usually a good, safe addition to soil.

What Can Go In A Compost Tumbler?

How Often Should I Turn My Compost Tumbler?

Leave a Reply

Your email address will not be published. Required fields are marked *