Nematodes microscopic worms, have gotten a bad name but most species are quite beneficial for soil. Bacteria, Fungal, Omnivores and Predator nematodes all contribute to a healthy soil ecosystem and protect your plant roots!

Pest Control: Something Unexpected

Improved Soil Health

Beneficial Nematodes

Bacteria Feeders

Fungi Feeders

Non-Beneficial Nematodes AKA Root Feeders!

Nematodes

Microscope: Basic Identification

Nematodes, often referred to as "roundworms," are microscopic worms. The ones found in soil are typically quite small, measuring less than 3 mm in length and only 15 to 100 µm in width, making them visible only under a microscope. Nematodes can be classified based on their feeding habits and are distinguished under a microscope by their mouthparts and internal organs. Each feeding group of nematodes plays a unique ecological role within the soil food web. There are five nematode feeding groups found in soil: bacterial feeders, fungal feeders, omnivores, predatory nematodes, and root feeders.

Nutrient Cycling

Nematodes play a significant role in nutrient cycling within ecosystems, primarily through their feeding activities and subsequent excretion.

How Nematodes Contribute to Nutrient Cycling:

Consumption and Mineralization: Nematodes feed on a variety of organisms, including bacteria, fungi, algae, other nematodes, and plant roots. When they consume these organisms, they ingest the nutrients contained within their bodies. However, nematodes have a different nutrient composition than their food sources. For example, bacteria have a higher nitrogen content compared to nematodes.
Excretion of Excess Nutrients: Because nematodes don't require all the nutrients they consume, they excrete the excess. This excretion process releases nutrients into the soil or surrounding environment in plant-available forms. This process is known as mineralization, where organic nutrients are converted into inorganic forms that plants can readily absorb.
Enhanced Decomposition: Some nematodes, particularly bacterial- and fungal-feeding types, can stimulate decomposition. By grazing on bacteria and fungi, they prevent these microorganisms from becoming stabilized in their own biomass, leading to a faster turnover of nutrients.
Nutrient Redistribution: As nematodes move through the soil, they can physically transport nutrients within the soil profile, contributing to a more even distribution.

Types of Nutrients Released by Nematodes:

The primary nutrient released in significant quantities by nematodes is nitrogen. Here's why and what form it takes:

Nitrogen (N): Bacterial- and fungal-feeding nematodes consume microorganisms, mosty bacterial that are rich in nitrogen. Since nematodes have a lower carbon-to-nitrogen ratio than bacteria and fungi, they excrete the excess nitrogen as ammonium (NH₄⁺). Ammonium is a readily available form of nitrogen that plants can uptake and utilize for growth.Studies suggest that free-living nematodes can contribute a substantial portion of the readily available nitrogen in the soil.
Phosphorus (P): While nitrogen release is the most prominent, nematodes also contribute to the cycling of other nutrients like phosphorus. When nematodes consume microorganisms, the phosphorus contained within those organisms is also processed. Some studies indicate that nematodes can enhance phosphorus availability in the soil, although the exact mechanisms and quantities may vary depending on the nematode type and the ecosystem. Further research and observation is needed.
Other Nutrients: To a lesser extent, nematodes can also contribute to the release of other essential nutrients like potassium, calcium, magnesium, and micronutrients as they break down organic matter and consume various organisms. These nutrients are released as part of the general mineralization process.
In summary, nematodes are crucial contributors to nutrient cycling, primarily by consuming microorganisms and releasing excess nutrients, especially nitrogen in the form of ammonium, back into the environment in forms that plants can use. This process enhances soil fertility and supports plant growth, making nematodes a vital component of healthy ecosystems.

Great Link for most information:

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nematode

Pest Control: Something Unexpected

Certain nematode species are natural predators of harmful insects and other soil pests. Beneficial, or entomopathogenic, nematodes are very effective at controlling several types of soil-dwelling insect larvae. Here are some key examples:

Grubs (Beetle Larvae):
- These are the larvae of various beetles, such as Japanese beetles, June beetles, and others.
- Nematodes, particularly those in the bacterial feeder Heterorhabditis genus, are very effective at targeting grubs in the soil.
- Grubs can cause significant damage to lawns and plant roots, making nematode control very valuable.
Cutworms and other Caterpillars (Moth Larvae):
- Cutworms are the larvae of certain moths, and they can devastate young plants by cutting them off at the base.
- Nematodes from the Steinernema genus are often used to control cutworms and other soil-dwelling caterpillar larvae. These nemadotes have a symbiotic relationship to the bacteria that grow or live on these specific larva which attracks them to these soil pests.
Weevil Larvae:
- Various weevil species have larvae that live in the soil and feed on plant roots.
- Black vine weevil larva are a common target.
- Nematodes can be quite effective against these pests.
Thrips larvae:
- While adult thrips damage foliage, many thrips species have larval and pupal stages that occur in the soil.
- Nematodes, especially Steinernema feltiae, are used to target these soil dwelling stages.

Beneficial nematodes play a crucial role in maintaining healthy soil, including the management of root-feeding nematodes.

Bacterial-feeding nematodes thrive in the rhizosphere, the area of soil directly surrounding plant roots, where sugars and other organic compounds are exuded. These exudates support a thriving bacterial community, which serves as the primary food source for bacterial-feeding nematodes. The presence of these bacteria can indeed signal the presence of plant roots to the nematodes.

Predatory nematodes, another important group of beneficial nematodes, actively hunt and consume root-feeding nematodes, providing a direct form of biological control.

Furthermore, soil conditions significantly influence the prevalence of different nematode types. Root-feeding nematodes often thrive in compacted, poorly aerated soils. In contrast, bacterial-feeding and many other beneficial nematodes prefer well-aerated, aerobic soil.

Maintaining good soil structure with adequate aeration creates an environment more favorable to beneficial aerobic organisms nematodes

Conversely, compacted soil can create conditions where root-feeding nematodes have a competitive advantage, making plants more vulnerable to their damage."

Key points about these nematodes:

They work by entering the insect larvae and releasing symbiotic bacteria that kill the host.
They are considered a biological control method, which is often preferred over chemical pesticides.
It is important to apply them under the correct environmental conditions, such as adequate soil moisture.
Keep soil covered, limiting tilling practices and keep moist.

Improved Soil Health

Regulation of the Soil Food Web: Predatory nematodes feed on other nematodes, as well as protozoa and microarthropods. This predation helps to regulate the populations of these organisms, preventing any single group from becoming dominant and potentially disrupting the balance of the soil food web. A balanced food web is crucial for overall soil health and function.

Enhanced Decomposition through Fragmentation and Distribution: While bacterial- and fungal-feeding nematodes directly contribute to nutrient release, their feeding activity also physically breaks down organic matter into smaller pieces. This increases the surface area available for decomposition by bacteria and fungi, accelerating the overall process. Furthermore, as nematodes move through the soil, they can carry bacteria and fungal spores in their guts and on their surfaces, effectively distributing these decomposers throughout the soil profile, leading to more efficient breakdown of organic materials in different locations.

Suppression of Plant Diseases (Indirectly): Some predatory nematodes feed on plant-parasitic nematodes, thus acting as natural biological control agents. By keeping populations of harmful nematodes in check, they contribute to healthier plant roots and reduce the incidence of soil-borne plant diseases, which is a key aspect of healthy soil.

Improved Soil Structure through Burrowing and Aggregate Formation (Indirectly): Although not their primary role, the movement of nematodes through the soil creates tiny channels and pores. This can indirectly contribute to improved soil aeration and water infiltration. Additionally, the excretion products of nematodes, along with their dead bodies, contribute to the organic matter content, which is essential for the formation and stability of soil aggregates, leading to better soil structure.

Serving as Bioindicators of Soil Health: The diversity and abundance of different types of nematodes in the soil can provide valuable information about the overall health and condition of the soil ecosystem. Changes in nematode communities can indicate shifts in nutrient availability, pollution levels, or the impact of different management practices. This makes them useful indicators for assessing and monitoring soil health.

Overall, beneficial nematodes contribute to a thriving soil ecosystem by promoting nutrient cycling, controlling pests naturally, and improving soil health, all of which lead to healthier plants.

Beneficial Nematodes

Bacteria Feeders

Fungi Feeders

Omnivores Feeders

Predatory