What do Soil Organisms Do?
We’re all aware that our soils are teeming with life, from the microscopic (bacteria) to the macroscopic (earthworms). In this post, we’ll examine some of the common soil organisms and discuss what they do in the soil.
First, the players. Here’s a list of common soil organisms. Keep in mind that the soil ecosystem is extremely varied and small changes in common soil characteristics (pH, water, temperature, nutrient levels) can have a large impact on the species found in the soil.
- Bacteria – both aerobic and anaerobic. As many as 100,000,000 bacteria per teaspoon of soil.
- Fungi – singled celled and multi-celled. Several yards per teaspoon.
- Protozoa – one celled animals. Several thousand protozoa per teaspoons of soil.
- Nematodes – also called roundworms. 10-20 nematodes per teaspoon of soil is typical.
- Arthropods – includes insects, spiders. Several hundred per cubic foot.
- Earthworms – One inch or more long. healthy soils will have 5-30 earthworms per cubic foot.
As you can see, healthy soils contain a wide variety of soil organisms. From simple single celled organisms, to more complex organisms like insects and earthworms.
The Value of Soil Organisms
From a farming perspective, a diverse active population of soil organisms has four main benefits; nutrient cycling, enhancing soil structure, enhancing plant growth, and controlling plant disease. Each of these benefits could be a topic on their own. I’ll just summarize the benefits here.
Nutrient Cycling – Probably the most important from a farming perspective, soil organisms help store nutrients in the soil and create new organic nutrients. Soil organisms are continually transforming and recycling nutrients. The key tasks of decomposition, mineralization, immobilization, and mineral transformation are all performed by soil organisms.
Enhanced Soil Structure – Crumbly, well aerated soils tend to support the most crops. Soil organisms are the key component of soil structure.
Enhanced Plant Growth – Beneficial soil bacteria and beneficial soil fungi produce a wide variety of plant hormones. These hormones stimulate plant roots.
Controlling Plant Disease – Soil organisms have a wide variety of ways to deal with plant predators. Some of the microscopic organisms complete with pathogens for food sources. Insects and protozoa tend to consume some of the harmful plant organisms, keeping their populations in check.
Each type of soil organism fits a unique niche, playing a different role in nutrient cycling, enhanced soil structure, and controlling plant diseases and plant predators.