How To Use Compost When Planting Tomatoes

Compost is a great material to use with your tomatoes to ensure they grow healthy and delicious. Using compost as a fertilizer can help your tomato plants thrive by providing vital nutrients. So, let’s talk about how to use compost for your tomatoes. 

You can use compost when planting tomatoes by using a 50/50 ratio of soil and compost. Mulch and compost tea can also help provide the right nutrients for your tomato plants when you use compost. Also, ensure your pile is ready before using it. 

Let’s discuss these tips in more detail and get your tomatoes growing healthy in no time. 

1. 50/50 Ratio for Soil and Compost

The first step to using compost when planting tomatoes is finding the right soil ratio to compost. Usually, 50/50 works well enough to allow the nutrients from the compost pile to balance with the nutrients from the soil. 

So, you may be wondering why you can’t just use all compost and no basic soil to plant tomatoes. The answer to this is simple, too much of a good thing isn’t necessarily healthy. You should be getting a good amount of vitamins every day, but too many vitamins aren’t good for you. Well, the same goes for composting. 

The main concern of using too much compost comes from phosphorus. Too much phosphorus can prevent your plant from being able to absorb iron which can result in iron-deficient plants. So, there must be some sort of balance with how much compost you use. 

What makes 50/50 such a good ratio for compost and soil is that it is easy to follow and can help ensure that your tomato plants benefit from both. So, remember to use a ratio when fertilizing your tomatoes with compost to prevent oversaturation of the nutrients in the compost pile. 

2. Use Mulch 

Using mulch can help your tomato plants in many ways. First, mulch is a great tool for keeping weeds at bay. Weeds can pull nutrients from the soil around your tomatoes and prevent them from getting the nutrients and oxygen they need to thrive. Putting mulch down will halt the growth and spreading of weeds near your tomato plant. 

The reason it is beneficial to use mulch, as well as compost, is that the mulch can add thickness that your compost pile doesn’t have. A good compost pile should be relatively smooth without large chunks of materials. In fact, this is how most composters know their pile is ready to use. So, a good compost pile won’t have any chunky material in it. 

Looking for the absence of chunky, solid material is one of the easiest ways to determine if your compost pile is ready to use or needs more time. If you want to know more about determining whether or not your compost pile is ready, check out my other article, which talks about the consistency to look for: How to Test Your Compost to Know If It’s Ready

Since your final compost pile lacks chunky materials, the sun will have more access to the soil around your tomato plant. This means that your plant is more likely to dry out as the soil around the plant will also be dry. This is where mulch comes in.

Mulch placed on top of the soil around your tomatoes can help limit the sun’s reach and allow the soil to hold moisture better. This will help your tomato plants have more access to water as they need it rather than drying out under the sun’s harsh heat. So, using compost does not erase the need for mulch. 

3. Compost Tea

If you want the most successful compost for your tomatoes, then you should consider compost tea. Let’s start with the basics. Compost tea is a liquid blend of organic material that you can create in many different ways. It is available for purchase, or you can make it yourself using composting materials from your pile. 

There are many different ways to make your compost tea, just like there are different ways to go about composting. It can be an intricate process for beginners. So, don’t be afraid to buy some already made if you don’t have time to learn the process. But if you do have time, learning how to make compost tea can have many benefits. 

A study done in Italy over the span of two years determined that compost tea had positive effects on the growth of tomatoes. In the study, compost tea produced more overall tomato plants. And these plants were more healthy compared to those without compost tea. Compost tea also helps tomato plants avoid common diseases that can plague your garden. 

What this study and other experienced composters will tell you is that compost tea is well worth the effort. Not only did the tomatoes in the study grow to be healthy, but there were also more of them overall. So, combine compost tea with your compost soil to get the most out of your tomato plants. 

4. Make Sure the Compost Is Ready

We touched on this a little bit in a previous section, but we can’t overstate the importance of using only compost that is ready to go. If you don’t let your compost pile finish, it can harm the soil more than it helps. As compost finishes the decomposition process, it needs a lot of nitrogen to keep going. So, unfinished compost can pull nitrogen from your plants. 

Adding unfinished compost to your tomato plants can cause them to be nitrogen deficient and even die before the compost finishes decomposing. The composting process also involves the release of amino acids to help the process of breaking down the materials. If you use your compost pile before it finishes, these amino acids can spread and damage nearby plants. 

Compost becomes less acidic and more neutral as the composting process finishes. So, using compost that isn’t ready can introduce these acids to your tomato plants. While some amino acids can benefit tomato plants, too much exposure can harm them. So, it is best to ensure that the pile finishes decomposing and becomes neutral before introducing it to your tomatoes.  

5. Monitor What You Put Into Your Compost

Tomato plants quickly absorb the nutrients from your compost right away. So, finding the right balance of nutrients is vital as tomato plants will absorb all of them rather than just what they need to survive. This makes a balanced compost pile absolutely vital in the growth and well-being of your tomato plants. 

You will need the right combination of brown and green materials in your compost to ensure it is as healthy and beneficial to the soil as possible. The idea is to balance the carbon and nitrogen in your pile. You can add carbon to your pile from brown ingredients like dried leaves and dried grass. These ingredients help provide carbon and avoid too much moisture. 

The green ingredients add nitrogen to your compost pile. These ingredients can include fresh leaves or fresh vegetable scraps. While these are equally as important as brown ingredients, you actually need less of these than brown ingredients. So, you need to find the right ratio for using browns and green ingredients to ensure the compost pile is healthy and nutritious. 

If you are composting for the first time, there is no harm in trying some different combinations to see what works best for you. Once you find the right combination of ingredients for the perfect compost pile, it will come easily to you afterward. So, try different combinations of composting materials and remember the ones that work best for you. 

Once the perfect compost pile is ready to go, you can add it to your tomato plants. Remember that compost piles that lack nutrients or are not complete can hurt your tomato plant more than help it. So, always ensure your pile is ready to use before putting it on your tomato plants. 

Final Thoughts

Overall, compost can help you grow the best possible tomatoes in your garden. If you use composted soil as well as compost tea, your tomatoes will flourish. Not only will you notice that they are healthy, but there will also be more overall as the soil will properly feed them. 

So, don’t be afraid to use your compost for tomato plants to ensure they are healthy and thrive in your garden. Always ensure that the composting process is complete before adding it to your tomatoes.

If you want to learn more about improving soil for tomatoes, you can check out my other article here: How to Improve Soil for Tomatoes (DIY Guide)

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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