The soil ecosystem is a fascinating mix of living and nonliving things, with microorganisms in the nutrient cycling process. It is a home crammed with millions of organisms.
Billions of bacteria, thousands of protozoans, and miles of mycorrhizal fungi live in just a teaspoon of healthy soil. Learn how these critters work together to break down organic matter and provide nutrition to plants.
1. Bacteria
A random handful of soil could contain up to 5000 different kinds of organisms, including bacteria, fungi, protozoa, nematodes, arthropods and earthworms. While these creatures are often overlooked, they are crucial to life in the soil. The bacterial community in a healthy soil provides a host of benefits, such as breaking down organic matter to provide nutrients for plants, creating good soil structure, and limiting the need for watering and erosion.
Bacteria are the largest group of microorganisms in the soil. They are a part of the soil food web, decomposing and recycling organic matter and feeding on sugars released by living roots. Their work makes it easier for plant roots to absorb essential nutrients like nitrogen, phosphorus and potassium. In addition, they help to form a strong and stable soil structure that prevents excessive water runoff, reduces nutrient leaching, and improves aeration.
These microorganisms can be found in all types of soil, but are most abundant in soil that is rich in organic matter. This is because they thrive in the presence of a diverse range of other organisms, which help to break down and decompose dead material, making it more readily available for plants to use.
The bacterial community is so important to soil health that it has been called the most biodiverse habitat on Earth. Its diversity helps to create the soil food chain, which allows for the natural recycling of nutrients within the soil and promotes a strong root system.
Soils rich in organic matter, such as those grown with a living soil practice, are characterized by the proliferation of beneficial microorganisms and mycorrhizae fungi. Mycorrhizae are a group of fungi that grow in a symbiotic or mildly pathogenic relationship with the roots of a plant, drawing fungi from the surrounding soil into the roots. This relationship is vital to the transfer of nutrients and water from the roots to the rest of the plant, as well as reducing water stress.
2. Fungi
Fungi are a critical component of the soil food web. Without healthy fungi, your garden will not be able to grow. Unlike bacteria which are single-celled and only visible to the naked eye, fungi exist as a massive network of microscopic filaments which can extend underground for miles, forming dense networks between soil particles. Most people are familiar with the above-ground portions of some fungi (such as mushrooms, mildew and bracket fungus) but this is merely their fruiting bodies, and only a small fraction of a fungus’s entire body.
Fungus is the major decomposer of organic material in the soil and breaks it down into its components, releasing nutrients in a form plants can use, a process called nutrient cycling. They are also responsible for transferring carbon from the atmosphere to the soil, through a process known as carbon sequestration.
They spend more time 1 on 1 with plant roots than any other microbial organism, in a process known as mycorrhizal relationship. Roughly 80% of all plant species have this relationship, where fungi form a network of hyphae that link up with the roots of vascular plants, helping them absorb water and minerals from the soil.
Fungi can be found growing in a variety of ways, from decomposing organic matter to breaking down the skins of invertebrates like insects and arthropods – including spiders, mites, ants and earthworms. They also play an important role in preserving the integrity of a soil’s structure, protecting against erosion and flooding. They are also key to maintaining soil health, as they help keep the soil loose enough for a dynamic mix of microorganisms and plants to thrive. Fungi are particularly vulnerable to the ill effects of over-fertilizing or applying herbicides and pesticides, and they require the proper balance of other microorganisms for optimum functioning.
3. Protozoa
If you were to look under a microscope, you’d discover soil teeming with life. Living organisms like bacteria, fungi, protozoa, nematodes and earthworms form an intricate web that decomposes organic matter, recycles nutrients and improves soil structure. This creates a self-sustaining medium that supports healthy plant growth, naturally.
Scientists and conservationists often measure soil health by measuring the following qualities:
Organic matter content. Healthy soil is rich in organic material that helps keep the microbes active & provides nutrition for the plants. This also helps with aeration and water retention which is essential for plant roots to breathe.
Water-holding capacity. The ability of the soil to retain moisture helps prevent excessive evaporation & drought stress.
Soil permeability. Healthy soil is porous with a network of both macropores (larger holes) and micropores (smaller pores). The larger pores allow for easy infiltration of water & air. The smaller pores help with nutrient cycling.
The more pore space in your soil, the better it is for root growth and overall health of the plant. Living soil practices also have positive economic impacts by reducing the need for expensive fertilizers. In addition, it reduces environmental costs by sequestering carbon in the soil as organic matter & trees. This reduces the amount of CO2 in the atmosphere, thus lowering the greenhouse effect and climate change. As the demand for organic & sustainably-produced food continues to grow, living soil practices offer a promising approach to sustainable agriculture. We encourage you to learn more about this exciting growing method and how it can help your cannabis crops thrive.
4. Earthworms
A gardener loves seeing earthworms slithering around in the soil, but they aren’t the only sign of healthy soil. They help “turn” the soil, bringing down organic matter from the top and mixing it with the soil underneath. Earthworms also make wonderful fertilizer. In fact, 500,000 earthworms in an acre of soil can make enough worm castings to fill up 100,000 one-pound coffee cans!
Like other decomposers, earthworms recycle organic material by ingesting it and incorporating it into their burrows. They process about two to twenty tons of organic matter per hectare each year in pasture soils, and they recycle about a similar amount in forest ecosystems.
In addition, earthworms aerate the soil by consuming and burrowing through it. In garden and farm ecosystems, they aerate and help release nutrients to crop plants; in forest ecosystems, they work with other decomposers to break down leaf litter, which supplies nutrients to trees and other vegetation.
Earthworms have special structures called setae that help them move through the soil, especially over rough surfaces. These bristle-like projections are located on each segment of the earthworm’s body, and they also have special cilia (little hairs) that help them sense movement in the soil.
All these organisms, and many more, work together to form a living soil. There is constant interaction among them; some, such as bacteria that live inside the earthworm’s digestive system, help to decompose organic matter; and other organisms, such as nematodes, feed on these bacteria or fungi, or both. The nematodes, in turn, help to protect the earthworms from predators. The diversity of all these organisms in the soil provides the nutrients that plants need to grow.
5. Nematodes
A teaspoon of soil may contain 5000 different kinds of creatures. This world of long-overlooked biodiversity is crucial to the functioning of healthy soils.
While some microorganisms are harmful, others provide valuable benefits to humans and other organisms that use the soil. Those that directly benefit us include earthworms, fungi, and nematodes. Nematodes are microscopic roundworms that inhabit virtually every ecosystem on the planet. While some species of nematode are pathogenic to plants, most are beneficial predators that play important roles in ecological balance.
When nematodes are introduced to a crop field by natural means, such as invading birds or earthworms, they can be effective tools for controlling pests without the use of chemicals. For example, a nematode known as golden cyst nematode can be used to control a serious potato pest called Leucanthemum tuberculosum, saving millions of dollars in annual crop losses.
Biological control nematodes are available for gardeners to purchase by mail order or at garden centres. These nematodes are sold in packs that are mixed with water and sprayed on the soil surface, usually around plant roots. Ideally, they are applied when the soil is cool and damp.
The nematodes are then allowed to move through the soil and infect insect prey such as slugs, chafer grubs, or leather jackets. As the nematodes consume insect bodies, they produce infective juveniles (IJ) which leave the cadavers and search for other insect hosts. The number of IJ produced varies depending on the specific species of nematode. The diversity of nematode species is important because they have different life history characteristics and occupy different microsites within the soil, which helps ensure complementarity and continuity of services.
