Nematodes: The Unsung Heroes of Composting
Numerous factors are at play inside a compost pile, including aeration, moisture, temperature and time. It all comes together to transform grass clippings, fruit scraps and coffee grounds into inorganic nutrients and organic matter. Microorganisms and invertebrates are an essential part of this process, doing much of the heavy lifting in decomposition. One of the hardest working invertebrates is the nematode, a microscopic worm that plays a critical role in recycling nutrients into soil.
Despite being one of the most abundant animals on earth — a square yard of soil can contain millions of nematodes — these creatures can be overlooked when it comes to their impact on composting, gardening and farming. Let’s take a closer look at nature’s most prolific decomposer and their role in turning waste into nitrogen- and carbon-rich organic material.
What Role Do Nematodes Play in Composting?
The vast majority of nematodes found in compost piles are free-living nematodes. Unlike plant-parasitic nematodes, free-living nematodes are beneficial for accelerating decomposition. Depending on their classification, these nematodes play a number of important roles related to compost health, including recycling minerals and making them accessible for plant roots.
Bacterial-feeding and fungal-feeding nematodes release excess nitrogen in the form of ammonium, which is made available to plants through microbial grazing. Predatory nematodes also contribute to nitrogen mineralization by preying on other nematodes. Additionally, predatory nematodes regulate the balance of various microorganisms, preventing overgrazing that can harm plants. Without nitrogen, plants are unable to conduct photosynthesis and eventually die, so the nematode’s ability to release plant-available nitrogen is particularly important. However, “decomposer” is just one of the many roles this microscopic worm plays.
Nematodes distribute bacteria and fungi throughout compost, carrying them either in their digestive systems or on their surfaces, and provide a source of food for other composting invertebrates, such as centipedes, mites and fly larvae. Nematodes can even prevent disease by preying on disease-causing organisms. They are such an intrinsic part of composting that nematodes have been used as bioindicators for soil health and compost maturity.
Nematodes as Indicators of Soil Health and Compost Maturity
One study on the role of nematodes in soil health asserts that it makes ecological sense to use nematodes as a bioindicators of soil condition because of their central position on the food web and critical connection to nitrogen cycling and plant health. Another study on nematode community in compost takes things a step further: Researchers found that during the decomposition process, bacterial-feeding and fungal-feeding nematodes constitute the majority of the nematode population, while predatory nematodes dominate during the late stages of decomposition. Finally, fungal-feeding nematodes are present during the most mature stage of decomposition. Essentially, compost maturity can be determined by the type of nematode most dominant at that time.
We’re not suggesting that you try to gauge compost maturity by counting nematodes one by one with a microscope. However, it’s important to illustrate how essential these tiny worms are for soil and plant health.
Fighting Nematodes With Nematodes
Although free-living nematodes are essential for decomposition, plant-parasitic nematodes present some serious agricultural challenges. Most plant-parasitic nematodes feed on plant roots, while others burrow directly inside of them. One particularly nasty nematode known as the root-knot nematode injects hormones into plant roots, causing them to twist and become grotesquely knotted. Damaged root systems are unable to absorb water and nutrients from the soil, and plants affected by plant-parasitic nematodes may become yellow, withered and stunted as they slowly die. Not even below-ground vegetables, such as carrots and potatoes, are safe from plant-parasitic nematodes.
Fortunately, you don’t have to worry about these pests in your compost pile, since plant-parasitic nematodes need a living plant to prosper. However, your compost pile could be the solution for soil already infested with plant-parasitic nematodes. Compost and other organic amendments prevent nematode damage by improving soil structure and suppressing nematode populations. By composting, you’re not only providing plants with vital nutrients, you’re also altering the composition of an entire microscopic community.
There’s very little you need to do to your compost pile to ensure that nematodes have a healthy environment to grow in. Just be sure to exclude any roots or diseased plants when adding waste materials. When it comes time to add compost to your garden, you’ll have thriving community of nematodes ready to recycle nutrients back into the soil.
Although nematodes play a critical role in making minerals available for plants, there’s still very little we know about nature’s most abundant animal. At the University of Florida, our Entomology and Nematology Department is hard at work uncovering the secrets of these microscopic organisms. If you’re interested in learning more about one of the most influential organisms in composting, gardening and farming, apply to one of UF’s online entomology and nematology programs and turn your backyard hobby into a rewarding career.