Will Fertilizer Kill Worms in Your Garden?

Worms are important to gardens because they can help improve the health of the soils. Many people also use fertilizer in their gardens since fertilizer can provide nutrients to plants. Suppose you want to use fertilizer in your garden—is it safe to use it if you also want worms in your garden?

A fertilizer will kill worms in your garden, especially a synthetic blend and an ammonia-based fertilizer. That means fertilizer is not safe to use if you want worms in your garden. If the fertilizer doesn’t kill your soil’s worms, it may decrease the likelihood of worms being present. 

In the rest of this article, I’ll talk about why fertilizer can harm and potentially kill worms in your garden. I’ll also discuss which fertilizers are safest and if you would like to keep your worm popular high. Keep reading.

Which Fertilizers Kill Worms?

There are so many excellent fertilizers on the market today that help various plants. However, sometimes fertilizers can help the aesthetic of plants but harm the soil in the long run. 

Ammonia-based fertilizers tend to harm and kill off earthworms in the soil because the soil’s pH level will lower and alter. Worms will leave the environment due to toxicity, or they may die from direct contact.  

Most fertilizers are safe for gardens and don’t harm the living organisms that exist in the soil. However, many synthetic blends and toxic fertilizers are harmful to live organisms in your soil because they contain ammonia. 

The component, ammonia, is a natural gas that is present in fertilizers and organic matter. Due to this, it isn’t bad but can be very toxic and unhealthy if derived from the wrong sources. 

And, for many, the worm population is very important for their garden. If gardeners want to preserve worms in their soil, it’s best to choose a fertilizer that supports the soil, as discussed below:

  • It doesn’t have toxic ammonia. Many fertilizers on the market are ammonia-based and can lower a soil’s pH level over time. This can harm the nutrients and living organisms in the soil, helping plants thrive. Gardeners should find a fertilizer that is simple and has clean ingredients, even if it’s a synthetic blend. 
  • The fertilizer promotes balance. Gardeners should find a fertilizer that’s balanced in nutrients and can supply soil and plants with the proper acidity and dosage amounts for success. Slow-release options are great. 
  • It’s an organic blend. Organic blends are safest for preserving the health of the soil, even though they don’t produce the fastest results. In the long term, they’ll help plants and soil thrive. 

Recommended Organic Fertilizers 

Many tend to stray away from using an organic fertilizer because organic fertilizers take time to produce results. However, organic fertilizers are the best option for preserving a worm population. 

Organic fertilizers will promote health and wellness in soil, and worms will actually thrive with these types of fertilizers. The pH levels and nutrients in the soil will also remain balanced. 

I recommend using organic fertilizer that preserves the organisms in your soil, such as bone meal, all-purpose organic fertilizer, or alfalfa meal fertilizer.

Are There Any Synthetic Blends That Are Not Ammonia-Based?

There are so many great organic options on the market that are free from ammonia. However, synthetic options tend to be more popular in today’s world. They’re simple to use and produce incredible results. 

Unfortunately, there are few to no synthetic blends that are free of ammonia. Most commercial fertilizers contain nitrogen, and ammonia is the gas that helps release nitrogen into the soil. 

Using a synthetic fertilizer with ammonia a couple of times is not going to harm your soil horribly and destroy all worms. However, it is going to lower the acidity in your soil. This is where the biggest harm will occur. 

If you would like to use synthetic fertilizer, it is best to find one that is simple. Here are a few things to look for: 

  • Find a fertilizer that has low nitrogen. 
  • Find a fertilizer that has high-quality ingredients. 
  • Use additives or simple ingredients rather than a blend.

Why Are Worms Important for the Soil?

Gardening is a fun process. However, it seems like insects and bugs tend to get in the way at times. The good thing is that soil actually thrives when certain bacteria and living organisms are present. 

Worms are important for the soil because they improve the condition of the soil, making it easier for plants to thrive. They help balance out the acidity, compaction, and water tension, and they protect the soil from harm. 

Worms love the soil and are completely harmless. They are also a great asset for gardeners to support because they are very helpful. 

Supplying soil with the right ingredients is valuable because it can increase the number of worms present. Worms can actually use organic fertilizer as food; they can adapt.

Keeping your fertilizer simple and free of toxins can help attract worms, and it can aid your soil with many components: 

  • The acidity of the soil will remain balanced.
  • The nutrients will be plentiful. 
  • Your soil will remain hydrated. 
  • Your plants will nourish and create a strong root system.

Having healthy soil can also attract other insects besides worms that are beneficial for your garden. Here are a few:

  • Ladybugs 
  • Bees
  • Dragonflies
  • Butterflies 
  • Lady Beetles

Is It Good To Have Many Worms in the Soil?

Many people are not fans of worms or bugs in general. Bugs tend to bug people, they bite, and they cause issues. However, worms don’t bug people like insects do and can be very helpful in the right environment. 

It’s good to have worms in the soil because worms burrow and move around the soil, creating water filtration and improving airflow. Additionally, they help create positive interactions in the soil for plants. 

As we know, worms love the soil, and they are very beneficial for gardens. However, gardeners might not be used to seeing many worms in a garden. 

The main reason people desire worms in their garden is that they help the quality of a garden. Worms naturally help combine minerals with organic matter. This can aid with the movement of nutrients in the soil so that plants can have an easier time feeding. 

If your soil is in great condition, then you will most likely have a large population of worms. Seeing worms in your garden is a positive sign. However, if worms are not present in your garden, that does not mean your garden is not flourishing. 

Can Gardeners Purchase Earthworms for Their Soil?

Many may wonder if they can add worms into the garden to promote healthy soil, and although that is a great solution, it is not always needed. 

Gardeners can purchase earthworms for their soil, but it is not needed because worms will come naturally. Purchasing worms is common for gardeners who are planting a garden in a garden bed. 

Gardeners often stress about their gardens. They desire their plants to grow big and strong and have healthy nutrients. And many are drawn to the idea of adding worms because they help the soil. 

However, gardeners don’t need to purchase worms because worms will come into the soil on their own in time. Worms might also find their way into your garden through certain blends of organic fertilizers and compost.

Do Worms Feed on the Organic Fertilizer Given to Plants?

As you may have known by now, organic fertilizer acts as a positive food for worms as well as soil. In fact, organic fertilizer can attract more worms into your garden. This can be a great thing, but it can also create worry in many gardeners. 

Worms feed on the organic fertilizer given to plants. But they also eat other things like decaying insects, dead leaves, bacteria, and fungi. The main source of a worm’s nutrients comes from dirt, grass, organic compost, and animal manure. 

Even in large amounts, worms will never create extensive damage to a garden. When gardeners first begin caring for their soil, having everything perfect is important, and worms might feel like a concern. 

However, worms will never excessively take organic nutrients away from the soil. If anything, worms help rid any bacteria that may create large issues in the soil. Besides the typical food sources that worms snack on, here are a few other sources they find nutrients from: 

  • Dead roots 
  • Dead grass 
  • Weeds 
  • Rotifers 
  • Protozoans 
  • Nematodes 
  • Bacteria 
  • Fungi 
  • Dead insects


Whether we like worms or not, they are positive for plants and soil everywhere. 

If you have worms in your soil, do your best to pick the right fertilizer. Your worms will thrive, your soil will be full of nutrients, and your garden will be plentiful. 

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, 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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