Please call it soil, not dirt. The rock, clay, minerals and silt that make up dirt are largely devoid of the organic matter and living organisms in the complex ecosystem that is healthy soil. In our newest workshop on creating healthy soil, in partnership with the Minnesota State Horticultural Society, local soil experts share practical knowledge on building the groundwork for healthy soil in your yard. The workshop offers numerous strategies well within the reach of most home gardeners.

Soil contains dirt, but it is also abundant with diverse life forms, from microscopic bacteria, mites, yeasts and algae to fungi, earthworms, beetles and other insects. In fact, there are more microbes in a spoonful of healthy soil than there are people on this planet. While we have much to learn, what we do know is that healthy soil is the foundation of a strong, resilient yard or garden. Among other things, it protects plants, captures carbon, filters and cleans the rain and prevents erosion.

The workshop introduces some of the inhabitants of this mysterious underworld and their role in the soil food web. Much of the activity happens microscopically, and takes place at the roots of plants, where bacteria and fungi exchange nutrition with plants and are themselves food for the predatory nematodes (tiny, tiny worms) and protozoa. Earthworms eat the protozoa. In turn, manure from all of this feasting fertilizes plants and provides more food for bacteria and fungi.

This non-stop activity builds structure in the soil. Healthy soil is full of space, with pores and corridors that provide habitat and air flow for organisms and plant roots. Bacteria and fungi make glue that sticks soil together, and branching fungal growths create even larger aggregates, forming soil’s structure.  The structure of healthy soil helps it to hold and slowly filter great amounts of water. In contrast, water often runs off of or sits on top of compacted dirt. In many places, soil management practices, including tillage and chemical use, have depleted the food web and broken down soil structure.

The good news is that we can take action to heal and protect the soil in our own yards. Here are some examples offered in the workshop:

• Cover your soil. Exposed soil is more vulnerable than soil under green cover. Imagine standing outside in a rainstorm without a raincoat or umbrella. You will feel it! When raindrops hit bare soil, they dislodge soil, causing compaction and erosion, and disturbing the inhabitants.
• Planting a groundcover protects your soil. Choose lower-impact landscaping practices. Stop tilling the soil, avoid fertilizers and pesticides and pull weeds by hand. Basically, reduce the disturbance to your soil to allow the ecosystem to work as it should.
• The idea of growing diversity above the ground also applies below the ground. A diversity of different root depths makes for a healthier soil ecosystem and better soil structure.

We are only beginning to scratch the surface in our understanding of the complex interactions happening right beneath our feet. But we have come to recognize with increasing clarity the importance of protecting our soil microbiomes.

— by Aleli Balagtas, Metro Blooms Reporter, aleli@metroblooms.org