Soil Microorganisms

As small as they are, soil microorganisms are the real giants in your garden, and your garden soil is swarming with billions of these microorganisms. This “living-soil-life” helps keep your soil healthy, decompose organic matter, replenish soil nutrients, form humus, promote root growth, increase nutrient uptake, and breakdown of herbicides and pesticides. These microorganisms include bacteria, algae, fungi, and protozoa.

Soil Protozoa and sand particle Soil Protozoa

Protozoa play an important role in nutrient cycling by feeding intensively on bacteria. Notice the size of the speck-like bacteria next to the oval protozoa and large, angular sand particle. Credit: Elaine R. Ingham (USDA) & Right Photo credit: Cells Alive

For soil organisms to increase and thrive in your garden soil you need to provide food and a healthy environment. The “food” can be provided with organic matter, and the best way a gardener can provide organic matter is in the form of compost and cover crops.

How to Help Microorganisms Thrive in Your Garden Soil

  • Minimize soil compaction. Seventy five percent (75%) of soil organisms are found in the top 2 inches (5cm) of soil.
  • Provide a lot of carbon-based food (organic matter) with green manure, mulch or compost.
  • Maintain a moist habitat.
  • Keep the soil oxygen content high with organic matter.
  • Do not let the soil go bare. Bare soil loses moisture, increases temperatures, and lacks organic matter.
  • Minimize soil disturbance. Use minimal tillage or no-tillage to minimize destruction of soil organisms and their environment.
  • Use organic fertilizers only.
  • Apply fertilizer in small doses and when the soil needs it.
  • Check the soil pH and modify it to keep in a range of 5-8.
  • Improve soils with poor drainage.
  • Rotate your garden crops or provide biodiversity with mixed species planting.

Most important, consider your soil's microorganisms as part of your complete garden ecosystem. These microorganisms will actively decompose organic matter and replenishes nutrients, ensuring soil and plant health.

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