MANY PEOPLE DON’T REALIZE THAT SOIL, 

ESPECIALLY HEALTHY SOIL, IS FULL OF LIFE. 

Many people don’t realize that soil, especially healthy soil, is full of life. Millions 

of species and billions of organisms make up a complex and diverse mix of 

microscopic and macroscopic life that represents the greatest concentration of 

biomass anywhere on the planet.

Bacteria, algae, microscopic insects, earthworms, beetles, ants, mites, and fungi 

are among them. All together, their value has been estimated at $1.5 trillion a 

year worldwide.

Estimates vary, but if you could weigh all the organisms in the top six inches of soil 

on an acre of land, you’d find they would weigh between 2,500 pounds to more 

than 5,000 pounds, depending on how healthy the soil is. That is a LOT of life.

What these low-lying creatures lack in size, they make up for in numbers. 

Consider bacteria, the soil microbes with the highest numbers, for example. 

You can fit 40 million of them on the end of one pin. In fact, there are more 

soil microorganisms (microbes for short) in a teaspoonful of soil than there are 

people on the earth.

These microbes, which make up only one-half of one percent of the total soil 

mass, are the yeasts, algae, protozoa, bacteria, nematodes, and fungi that 

process soil into rich, dark, stable humus.

Like other living creatures, the organisms in the soil also need food and shelter. 

Some feed on dead organic matter, and some eat other microbes. As a group, 

they cycle nutrients, build the soil and give it structure.

The healthiest soils are those with a diversity and abundance of life. Farmers with 

the healthiest soils nurture that life by creating a diversity of plant life above the 

soil surface, with year-round ground cover, no tillage, and judicious pesticide use. 

Understanding that the soil is full of life is a game-changer for farmers who are 

full of life.

Uni

Dep

Agr

USDA is an equal opportunity provider and employer.

HEALTHY SOILS ARE:

Natural Resources Conservation Service
Fully realizing the soil is full of life is a game-changer for producers who are farming 

with healthy soils in mind. For those producers, farming centers around feeding the 

organisms that build healthy soils. 

These farmers understand that tillage, the turning of the soil that has been the 

standard for growing crops for years and years, is disruptive to soil microbes and 

destructive to the soil system.

Instead, they disturb the soil as little as possible. And, they grow a diversity of living 

plants in the soil as much of the time as practical, covering the soil and offering 

food to soil microbes through living roots. Those soil organisms, in turn, cycle 

nutrients back to the plant, allowing it to grow and flourish. 

It’s a natural, symbiotic system that leads to healthy soils and more sustainable and 

profitable agriculture.

HEALTHY SOILS ARE: full of life.

WANT TO LEARN MORE? VISIT WWW.NRCS.USDA.GOV

ORGANISM WHAT DOES IT DO?

BACTERIA Feed on organic matter, store and cycle nitrogen, and decompose pesticides.

FUNGI Up to 3,000 species of fungi are in the soil. Some feed on dead organic matter 

like crop residues that are more difficult to break down–others are parasites that 

attack other microbes. Some fan out from the root to get more nutrients and hold 

more water for the plant, delivering nutrients to the plant in exchange for carbon.

PROTOZOA Eat bacteria, fungi, and algae. When they eat bacteria, their main food source, 

they unlock nitrogen that’s released into the soil environment slowly. They 

convert organic nitrogen to inorganic nitrogen that’s available to plants.

MITES Decompose and shred organic matter as an important part of the nitrogen cycle.

NEMATODES These microscopic worms are an important part of the nitrogen cycle. Most are 

non-pathogenic and don’t cause disease. They eat other organisms in the soil.

EARTHWORMS Expel partially decomposed organic matter, produce nutrient-rich casts, and 

make lubricated tunnels that aid soil structure and water movement in the soil.

Note: It’s important to know how these organisms contribute to building healthy soil, but it’s also important to know 

what harms them. Both tillage and the non-judicious use of pesticides can harm these important organisms.