Of Plants, Trees, and Soil: for Gardeners

by Elsa Johnson

What is soil  (dirt!)  (earth!) – you know, that stuff plants (most of them) grow in — and how important is it, anyway?  

I’ll answer the second question first. Very important. At its simplest, soil is the stuff that feeds the green plants that create the atmosphere of our blue-green planet.  Soil is a creation, a product, the end result of a process.

We humans have a ‘thing’ for order and neatness. It is one of the ways we distinguish between the tended (hence, civilized; hence, reassuring) and the untamed (hence, wild; hence, threatening). It is the drive that compels us to pull up every unwanted plant, to prefer bare soil to – god forbid — a ‘mess’, to throw every bit of organic debris into a recycling bag for the city to come and fetch and take away.

Plants pull nutrients from the soil – and plants also create nutrients through their growth process. This is what we see above the soil – the growing plant and the soil around it. When the organic plant dies and decays in place, those nutrients go back to the soil, both above and below ground. With the help of insects and worms that take from the plant what they need for their own survival as they break down the plant’s fiber, this natural process builds a loose layer of topsoil. Soil is creation. We can help or hinder that. We all know that. But in the garden we have a hard time resisting our human need for order, for that look-of-civilization –and so, far too often, we take away all that good organic stuff that, if left, would enrich and rebuild our soils (for free) without doing any harm.  

In the forest the process works slightly differently. Tree leaves are fibrous and tough (if they weren’t we would be eating them). They don’t break down as easily or as quickly as soft-fiber garden debris. They decompose slowly, over a long time, resulting in a deeply layered forest floor of leaves in varying stages of decay, resulting in a deep, loose, dark duff under a natural leaf mulch that holds moisture and insulates the forest floor.

And this is just above ground.

Below ground soil is truly amazing, for in both the garden and the forest within that uninteresting looking ubiquitous soil exists a universe of diverse microorganisms, fungus, and bacteria with important jobs to do bringing nutrients, minerals, oxygen, and water to the roots of plants and trees. And a world of necessary microscopic predation goes on there too (for this is always the price life pays for life). That is healthy soil, sustained by and supporting the intricate, exquisite interrelationships of this complex, rich system. Intact, undamaged, these systems are self-sustaining. However, many of our common practices damage the soil.

All plants sequester carbon, as does oil, but exposing bare soil to air allows the soil to lose carbon into the atmosphere. Soil should be either planted or mulched.

Heavy equipment regularly and repeatedly rolling over the ground compresses soil, reducing its ability to absorb and hold oxygen and water, and also kills microscopic organisms that plants and trees need for health. Try to keep the use of heavy equipment to a minimum.  

Breaking up the soil by plowing or spading also loses carbon from the soil, and perhaps more importantly, breaks up soil structure, disrupting mycorrhizal structures and microscopic animals, and severing root connections and root interrelationships necessary for plant health.

Last — chemical fertilizers kill beneficial organisms, thus destroying soil health, and making plants dependent on repeat applications. Build soil health through composting and returning organic material to the garden.             

 

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