Microscopic Soil Life Means Macroscopic Soil Life

17 Jan

It is relatively common knowledge that having a diverse plant community drastically improves a farm or garden’s resilience to invasive pests, weeds, and disease. Having diversity, as opposed to a monoculture, makes it difficult for a plant-specific pest to wipe out an entire plot, bed, acre,…etc. As it turns out, diversity in the soil is just as important. Healthy soil is teaming with biological activity, much of it however, invisible to the naked eye. These microscopic soil dwellers are critical for the support and livelihood of the plants that share the soil with them.

Healthy soil is relevant for all humans on the planet. Whether you are a recreational gardener, a farmer, or just a consumer, healthy soil is key! Composting is not just an environmentally friendly way to deal with our consumer waste products, but the ultimate method for building healthy soil.

Compost has many wonderful functions in aiding soil health – chiefly, fostering a diverse and robust microbial community. But what do microbes do for our soil and ultimately the plants that sprout from it?

When organic matter in the form of compost is added to soil, the microbial soil community has an abundant food source. Plants naturally ‘know’ this and pump a portion of their home-made sugars made above ground via photosynthesis down to their roots, releasing what the scientific community calls ‘root exudates’:  sugars that feed and support the local microbial community. This creates a micro-society about the root called the rhizosphere (the soil in close proximity to the roots). The bacteria that live here are specifically called rhizobacteria and are generally plant growth-promoting. These rhizobacteria enhance nutrient uptake and help ward off plant diseases. In general though, soil microbes eagerly breakdown organic compounds and take all of that organically bound nutrient content such as nitrogen, phosphorous, and sulfur and makes them plant-available. Plants can take up nutrients only if they are in a certain form. Microbes promote such conversions. Hey, that’s pretty nice! This is a service that is purely a byproduct of the breakdown of the food they need to survive (organic matter).

The flow of nutrients. When organic matter is added to soil, microbes are the first players in breaking down the material and releasing nutrients in a plant available form.

The flow of nutrients. When organic matter is added to soil, microbes are the first players in breaking down the material and releasing nutrients in a plant available form. Image via ecoplexity.org

Other essential elements such as iron and manganese are largely controlled by microorganism activities. Microbes also protect plants from toxic levels of these elements by converting them to a form that is un-available to plants.

Ever wonder what gives healthy looking soil that good fresh smell? That would be the welcomed presence of actinomycetes. These are fungi-like bacteria. These feed off of decaying organic matter and have the important role of decomposing organic matter and liberating its nutrients. They also have the ability to breakdown tougher organic compounds (cellulose, chitin, and phospholipids) . They occur in the later stages of breakdown, since they can attack those more complex organic compounds. That’s why ready compost smells good. Thanks, actinomycetes!

The breakdown of organic matter into simpler sugars and such in turn provides glue-like organic substances for which to aid healthy soil structure. Good soil structure means aggregation: amorphous and diversely sized clumps of soil that remains stable under moist conditions. Aggregation simultaneously provides aeration, root pathways, and water retention.

There is much more that can be said about the importance of soil biology diversity, however the bottom line for soil health management points to one mantra: ADD ORGANIC MATTER.

Did you know that just a teaspoon of humus (organic matter, i.e. compost) contains more organisms than there are people on this planet? Yes, billions of microorganisms! So compost it up!

The WSU Master Gardener program as well as the Master Composter & Recycling program both teach various composting methods. There is still space in the Master Gardener 2013 class! Sign up, bring a friend! Drop by one of the following pre-orientations to find out more:

  • January 18th 10:30 AM – 12 PM
  • January 24th  4:30 PM – 6 PM

At the WSU Extension Office in West Olympia:

5033 Harrison Ave NW

Olympia, WA 98502

Questions about the WSU Master Gardener program? Contact program coordinator Cori Carlton: (360) 867 – 2162, or email her at carltoc@co.thurston.wa.us.

You can also visit our website at http://county.wsu.edu/thurston  Click on the “Master Gardener” heading.


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