Tiny Worlds: The Extraordinary Influence of Soil Microbes

Though invisible to the naked eye, these tiny creatures lead fascinating lives as architects, skillful hunters, community builders, escape artists, and travelers. They perform complex roles with global impacts — and many of them do it all within the elegant simplicity of a single cell.

Soil microbes carry out a multitude of microscopic processes that influence the Earth’s biosphere. They regulate nutrient cycling, affect climate patterns, sequester carbon, prevent soil erosion, filter water, and mitigate droughts and floods worldwide. In fact, many consider the interactions between the soil microbes, plants, and climate as the Earth’s most valuable ecosystem.

Scientists have identified more than 1 trillion different species of microbes. In fact, there can be as many as 10,000 to 50,000 different species within a single teaspoon of soil. As these organisms go about their business beneath the soil’s surface, living, eating, reproducing, and dying, their activities directly affect plant fertility.

Soil microbes:

• Improve soil structure by forming aggregate compounds,
• Consume organic substances to produce soil organic matter,
• Mineralize and solubilize nutrients like nitrogen and phosphorus and make them bio-available to plants,
• Are able to break down pollutants in soils, and
• Can make plants more resistant to stress.

Growers today recognize the value of farming in a way that supports the microbial life in the soil. Practices such as cover cropping, conservation tillage, crop rotation, and organic treatments are increasingly acknowledged for their ability to enhance soil fertility and support higher crop yields by nurturing a balanced and flourishing microbial community. For growers interested in boosting soil ecology, here are a few key microbial players to get to know.

Bacteria

Bacteria live in the tiny spaces and aqueous films around soil particles where they perform important functions related to soil structure, water dynamics, and nutrient cycling. Some bacteria produce substances that help bind soil particles into small aggregates that can improve water infiltration and the soil’s water-holding ability. Others supply plants with nitrogen.

Nitrogen-fixing bacteria form mutually beneficial relationships with plant roots. The plant supplies the bacteria with carbon compounds, and the bacteria convert nitrogen from the air into a form the plant can use. These organisms can be categorized as independent, free-living bacteria or symbiotic bacteria that colonize a plant’s root system.

Protozoa

Protozoa are the predators of the unicellular world. The word ​“protozoa,” in fact means ​“primitive, or original animals” — a reference to their animal-like hunting behaviors. They feast primarily on bacteria — a single protozoa can consume as many as 5 million bacteria in one day — but they also consume other protozoa, soluble organic matter, and fungi.

As they feast, they mineralize nutrients, making them available for use by plants and other soil organisms. Protozoa have a lower concentration of carbon and nitrogen in their cells than the bacteria they eat so they release the excess nitrogen in the form of ammonium near the root system of a plant.

Fungi

Fungi are unique organisms that can be unicellular or grow in long threadlike structures. For millions of years, plants have benefitted from a symbiotic relationship with fungi that colonize their roots, creating long root-like extensions. These fungal filaments, or hyphae, channel nutrients and water back to the plant and connect them through natural networks that enable them to communicate and interact with one another.

Fungal decomposers break down organic matter and support nutrient retention in soils, while mutualists such as Mycorrhizal fungi colonize plant roots, improving the plant’s access to water and nutrients and protecting roots from pests and pathogens.

The living soil, where we grow our food, is a complex ecosystem abundant with life and vital biological processes. Although we often take these tiny subterranean populations for granted, one of the greatest leverage points for our planet’s sustainable future is beneath our feet. By supporting the microbial communities in soil, we can capitalize on the interactions between plants and microbes to boost the nutrition available to crops, improve soil health, and enhance production yields. The impact of these vital microbial communities seems proof that in farming, the little things make a big difference.