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Soil biology

In most ecosystems, more life and diversity exists underground than above. The soil is home to a vast array of organisms, including bacteria, cyanobacteria, algae, protozoa, fungi, nematodes and mites, insects of all sizes, worms, small mammals and plant roots.

Role of soil organisms

Soil organisms play critical roles in plant health and water dynamics. Processes that soil organisms contribute to include:

  • Nutrient cycling.

  • Nutrient retention.

  • Water infiltration and water-holding capacity.

  • Disease suppression.

  • Degradation of pollutants.

  • Increasing the soil’s biological diversity.

  • Improving soil structure.

Soil biological processes are responsible for supplying approximately 75 percent of the plant-available nitrogen and 65 percent of the available phosphorus in the soil.

Like all organisms, those inhabiting soil need food and a favorable environment. Adequate organic matter content, ample aeration, moderate moisture, neutral pH and warm temperatures all favor increased microbial activity.

Benefits of organic matter

By maintaining a high soil organic matter content, food and a favorable habitat can be built for a diverse community of soil organisms. Not only does organic matter provide good habitat, but it also greatly benefits chemical and physical soil characteristics.

Moisture, pH, nutrient supply and the biological community are all more stable, or buffered, as soil organic matter increases. Organic material also helps maintain soil porosity, which is essential because most beneficial soil microbes and processes are aerobic, meaning they requiring oxygen.

Understanding soil biology


Management strategies

It’s important to remember the general philosophy that beneficial soil organisms need to be needed.

That is, if the farm system depends on and supports their activities, more biomass and positive activities will develop. If the farm system solely depends on chemical inputs instead of biological inputs, beneficial biomass and activities will decline.


Jodi DeJong-Hughes, Extension educator

Reviewed in 2018

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