Benefits of Earthworms to Soil Health

How do earthworms benefit the soil?

Plants and soil grass need correct soil conditions to thrive. So, how do earthworms contribute to this? Did you know earthworms are called a farmer or gardener’s best friends? Let us look at five reasons why earthworms are beneficial to the soil.

1. Earthworms increase soil fertility

Plants need nutrients to grow, just like humans need vitamins and a nutritious diet. Earthworms feed on plant debris and other organic matter like animal waste and manure. This diet of the earthworm implies that the digestive system of an earthworm gathers all the organic and inorganic nutrients and minerals from the soil around it, making the cast of earthworms rich in nutrients.

As the earthworms tunnel through the soil, they leave their casts which provide all the gathered nutrients to the soil. Soil Association states, “[Earthworm] casts can contain five times more nitrogen, seven times more phosphorus, and 1000 times more beneficial bacteria than the original soil..” Therefore, we can say that earthworms provide the soil with natural fertilizer that is rich in essential nutrients like nitrogen and phosphorus.

2. Earthworms improve soil drainage

Soils with poor drainage cause the roots of the plants and turfgrass to experience water stress due to waterlogging and puddles. Earthworms improve soil drainage by tunneling through the soil and loosening compact areas. This allows proper circulation of air, water and nutrients in the soil, which improves plant health. 

Also, research on soil biodiversity by the European Commission has shown that soils that have earthworms present in them are able to absorb 90 percent more water than soils without earthworms. Therefore, the presence of earthworms in the soil reduces soil and nutrient loss due to runoff.

3. Earthworms break down thatch

Thatch is a layer of living and dead plant debris (leaves, stems, roots, twigs) that forms between the layers of the grass growing above and the soil below. A thin layer of thatch (less than half an inch) is not harmful to the soil, but once it becomes thicker, it affects the drainage of the soil and prevents water and nutrients from reaching the roots of the plants or grass.

4. Earthworms improve soil structure

Soil structure refers to the way particles of the soil, whether sand, clay, or silt, are grouped together. The casts of earthworms cement or bind the soil particles to create heavier lumps called aggregates. Higher soil aggregate reduces soil erosion, decreases soil and nutrient loss due to runoff, and improves root penetration, moisture retention, and soil drainage.

5. Earthworms encourage the growth of deep root systems

As we have seen, earthworms loosen compacted soil with their tunneling and burrowing actions. Apart from aerating the soil, these activities are also beneficial in encouraging plants and turfgrass to develop a deep root system. When the soil is compacted, the roots of the plants are not able to penetrate deep into the soil, creating shallow root systems. Plants and turfgrass with shallow root systems are weak, unable to withstand harsh conditions and are not tolerant to drought, stress, weeds, pests, and diseases.

6. Earthworms are a source of food for other wildlife

While we have seen that earthworms are highly beneficial to soil health, we also need to understand how they impact the mini-ecosystem of your landscape. Earthworms might be lower on the food chain than most species, but that does not make them any less important. Earthworms are a rich food source for wildlife like birds and frogs, which are helpful in pollinating the landscape.

7. Earthworms help repair damaged or contaminated soil

Soils can get easily contaminated due to environmental and industrial pollutants, and this contamination can damage the soil by degrading its quality. Earthworms help fix this type of damaged soil through a process called bioremediation. Bioremediation is the process by which microorganisms break down contaminants and convert them into non-toxic particles, thus cleaning the soil and improving its quality. 

How can you encourage earthworms in your soil?

Earthworms thrive when the soil conditions are ideal for plant and grass growth. Therefore, a higher number of earthworms in your soil are an indication that your soil is in good health. So, how do you encourage the presence of ‘the ideal soil analysts’ like Michael Astera, the author of ‘The Ideal Soil,’ termed earthworms? Below are the different ways in which you can create ideal conditions to encourage earthworms in your soil.

• Maintain your soil pH between 6-7: Earthworms cannot survive in soils that are too acidic, and their preferred soil pH range is between 6-7, although they can tolerate a wider range of 5 to 8. 
• Increase organic matter in the soil: Earthworms feed on organic debris like leaves, stems, and roots, along with compost and manure. Therefore, increasing organic matter in the soil will attract more earthworms and encourage their presence in the soil.
• Keep the soil moist: Earthworms can lose around 20% of their weight daily in the form of castings and mucus; therefore, they need the soil to be moist to survive. 
• Reduce tilling and cultivation: Frequent and intense tilling and cultivation affects the earthworm population in the soil by damaging their eggs (typically laid at a depth of 5 cm), destroying their burrows, or directly killing them. 
• Improve soil drainage: Though earthworms prefer moist soil, they cannot survive in waterlogged soils. Therefore, Eden recommends improving soil drainage if your soil has a tendency to puddle to increase the number of earthworms in your soil.
• Reduce the use of chemical products: Chemical applications of fertilizers, pesticides and fungicides harm the earthworms in the soil. Pesticides can negatively affect the reproduction of the earthworms. Lastly, the fertilizers containing acidifying composition like ammonium sulfate affect the growing conditions of earthworms.
• Protect the earthworms from harsh climatic conditions: Earthworms cannot tolerate harsh climatic conditions like frost and drought, and therefore, you should stay on top of weather updates to take appropriate measures to protect them.
• Maintain soil temperature between 50 to 60 degrees Fahrenheit: Earthworms are cold-blooded organisms and therefore require a soil temperature of 50 to 60 degrees Fahrenheit to thrive.
• Ensure soil texture is ideal: Earthworms do not like soils that are too sandy and prefer loamy soil. Therefore, if your soil texture is sandy, you need to amend it to increase the soil’s clay content.

What kind of soil do earthworms prefer?

Earthworms prefer soils that are loamy and have a soil pH between 6-7; if the soil is too sandy, it will not retain moisture. The soil should have a high composition of organic matter, including manure and compost and should not be compacted. The soil should be able to retain moisture but not so much that it becomes waterlogged because they respirate through their skin, and too much water in the soil will drown them. Also, the temperature of the soil should be around 50 to 60 degrees Fahrenheit.

Are there any disadvantages of earthworms to the soil?

As we have seen in the above section, earthworms provide a lot of benefits to the soil, but we need to remember that too much of a good thing can be bad. While manageable numbers of earthworms are good for soil health, when there are too many earthworms in your soil, they can cause some problems. Below are the disadvantages of having excessive numbers of earthworms in your soil.

1. Earthworm castings can make your lawn look unsightly

When the number of earthworms increases, the amount of earthworm castings also increases. Earthworm castings are football-shaped and dark brown in color, and when too many of them are found in the yard, they can ruin the look of your otherwise well-kept landscape.

2. Too many castings can cause fertilizer burns

Earthworm castings or vermicompost are a rich source of fertilizer, and ideal numbers of earthworms increase the nutrient content of the soil. However, too many earthworm castings will add excessive amounts of fertilizer to some parts of the soil. This will cause the plants or grass in that area to slowly turn yellow due to fertilizer burn.

3. High numbers of earthworms can attract unwanted wildlife

Earthworms are a source of food for wildlife like gophers, moles and armadillos. If you do not contain the earthworm population in your yard, these animals will enter your carefully designed and maintained landscape and start tearing the soil apart in search of these earthworms. Thus, destroying all your hard work.

How to control earthworms in the soil?

If the earthworm populations are going out of control in your soil and harming your lawn more than benefitting it, then it is time to start controlling the number of earthworms in your lawn. Below are some ways to control earthworms in your soil.

• Employ biological control: Biological control involves introducing natural predators into your landscape to let nature do its job. Attract birds to your yard using bird feeders and birdbaths to feed on these earthworms and manage their numbers.
• Remove thatch: Dethatching it will take away one source of food for the earthworms and prevent them from increasing in number.
• Do not overwater your lawn: Earthworms rise to the surface of the soil to leave behind castings when there is too much water in your soil (like after it rains). Therefore, if you see this happening in your yard, you should adjust your watering schedule to ensure you are not overwatering your lawn.
• Reduce organic matter: As mentioned above, earthworms feed on organic matter like plant debris along with compost and manure. Therefore, reducing the amount of organic matter can work. 
• Remove the worms manually: After heavy rains, earthworms tend to come up to the surface of the soil due to the presence of excess water in the soil. When this happens, you can pick the earthworms and remove them from the yard manually. 

How to control earthworm castings on the lawn?

Dealing with earthworm castings is a minor consequence of introducing earthworms into your lawn to improve soil health. Given below are the ways in which you can control earthworm castings in the lawn.

• Rake the castings: Rake the castings from the lawn with a garden rake when they are dry to collect them. Once all the earthworm castings are collected, you can either toss them into your vermicompost pile or add them to your garden bed soil to provide free natural fertilizer.
• Mow your lawn high: Mowing the lawn high will hide the castings among the tall grass and keep the lawn healthy. This will minimize any effect the castings might have on the aesthetics of the lawn.
• Do not overwater your lawn: When there is too much water present in the soil, the earthworms tend to wiggle up to the surface of the soil and leave their castings in the open. Therefore, adjusting your lawn watering schedule to provide only the amount of water required by the lawn will keep the earthworms and their castings inside the soil where you can’t see them.

Earthworms are beneficial to the soil in many ways, but large numbers of them will harm the appearance of your lawn and cause an overload of fertilizer to the soil. If earthworms are taking over your lawn and you need to control them in ways that do not exterminate them or harm your lawn, contact Eden’s professional lawn care services.