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Friend or Foe? Nematodes in the Soil

Updated: Apr 5

Bacterial Feeding Nematode microscope image showing internal organs and mouth parts.
Bacterial Feeding Nematode

Beneath our feet lies a bustling ecosystem teeming with life. The soil, often overlooked, is a complex web of interactions that support life on Earth. One of the most fascinating and important members of this subterranean world is the nematode. Nematodes, tiny worm-like creatures, play a crucial role in the soil food web, facilitating nutrient cycling, decomposition, and even pest control. In this blog post, we will dive into the world of nematodes and uncover their invaluable contributions to soil health.

The Diversity of Nematodes

Nematodes are a diverse group of roundworms that inhabit a wide range of ecosystems. These microscopic organisms come in various shapes and sizes, with some measuring just a fraction of a millimeter, while others can reach several millimeters in length. There is an astounding diversity of nematodes, with an estimated 1 million species, many of which have yet to be identified. They live among the most extreme environments on Earth, from terrestrial, freshwater to marine, polar to tropical regions. Some estimates claim that nematodes make up 80% of all individual animals on earth, including 35 species that call the human body home.

Nematodes can be categorized by their functional group by what they eat: bacterial, fungal and root feeders, predatory nematodes, and omnivores. While root feeding nematodes have been known to cause crop losses, the vast majority of nematodes are beneficial. Most of the research on nematodes has been devoted to these few pathogenic species, and how to best kill them. Unfortunately, pesticides kill beneficial organisms as well. In a healthy Soil Food Web, predatory nematodes will keep the root-feeders in check.

Nematodes in the Soil Food Web

  1. Nutrient Cyclers: Nematodes are essential for nutrient cycling in the soil. They feed on bacteria, fungi, and other microorganisms, helping to control their populations and releasing plant-available nutrients.

  2. Predators: Predatory nematodes prefer to feed on harmful root-feeding nematodes. This biological control helps maintain a healthy balance in the soil ecosystem and reduces the need for chemical pesticides.

  3. Indicator Species: Nematodes are sensitive to changes in soil conditions, such as temperature, moisture, and pH. Monitoring nematode populations can serve as an indicator of soil health and quality. A diverse nematode community often signifies a well-balanced and fertile soil ecosystem.

  4. Decomposers: Some saprophage nematodes are primary decomposers, breaking down organic matter like dead plant material and releasing essential nutrients back into the soil.

Microscope image of nematode showing mouth parts
"Switcher" Nematodes mainly eat fungi, but will switch to roots

The Balance of Power

Maintaining a balanced nematode community is essential for a healthy soil food web. An imbalance can disrupt the intricate relationships within the ecosystem. For instance, an overpopulation of predatory nematodes can lead to a decline in other microorganisms, affecting nutrient cycling and potentially causing plant stress. Therefore, understanding nematode ecology and the role they play is crucial for sustainable agriculture and environmental management.

Conservation Strategies

To harness the benefits of nematodes and promote soil health, there are several strategies that can be employed:

  1. Reduced Chemical Inputs: Minimizing the use of chemical pesticides and fertilizers can help preserve nematode populations and maintain a diverse soil ecosystem.

  2. Crop Rotation: Implementing crop rotation can break the life cycle of plant-parasitic nematodes and reduce their impact on agricultural crops.

  3. Organic Farming Practices: Organic farming practices, such as cover cropping and composting, can enhance soil biodiversity, providing a conducive environment for nematodes to thrive.

  4. Soil Testing: Regular soil testing can help assess nematode populations and determine the need for specific management practices.

Orchard image, using ground cover crops
Orchard practicing cover crops and interplanting. Credit: AdobeStock


Nematodes are often overlooked or misunderstood, but are integral to the functioning of the soil food web. These tiny creatures contribute to nutrient cycling, decomposition, pest control, and overall soil health. Understanding and appreciating their role in soil ecosystems can lead to more sustainable and environmentally friendly agricultural practices. As we continue to explore the intricate world beneath our feet, let us not forget the microscopic friends of the soil—nematodes.

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