Did you know that the top foot of soil has more 7 to 50 times more life than the next 3 1/2 feet? (Source: Designing and Maintaining Your Edible Landscape Naturally by Robert Kourik, Metamorphic Press 1986). When soil is tilled or plowed, too much air is introduced all at once.
Life thrives in a zone of ‘enoughness’. Now I realize this is a foreign concept to most people, who as a rule want more, more, more of everything and then some. (This proclivity has led to such pop culture aphorisms like, “Too much of a good thing is just about right.”) Think about it though: more consumerism leads to more waste and more waste leads to more plastic waste as a proportion of that overall waste stream. More plastic waste leads to larger oceanic garbage patch gyres, of which there are currently five. But, I digress. More oxygen in the soil introduced like a shot of steroids does not lead to more life but to less. You may think you’re taking care of one problem – say for instance a pest outbreak – but you’re unintentionally creating a lot of new problems for yourself. You’re also destroying the soil’s structure, especially if you are tilling over and over from year to year. (There are techniques to aerate the soil less violently, but those may be introduced in later posts.)
Imagine taking a whole block of any given urban development – New York, Paris, London, Scottdale, Tokyo, Los Angeles – and upending that entire block, buildings, streets, and all. What used to be the tops of buildings are now underground and beneath everything else that used to be above them. Don’t you think that would be quite disruptive, to say the least?
Turning the soil is no less deadly. Soil flora and fauna tend to live in specific strata in the soil and tillage disrupts this order. For instance, there are some native California earthworms (yes, they exist! – check out this paper) that tend to tunnel deeply and other species that live closer to the surface. If you’re smart and letting nature do the heavy lifting for you, the only creatures that are turning the soil the vast majority of the time are earthworms and other ground dwelling animals that tend to tunnel. You may not like the affect these creatures have on the visual appearance of your landscape or your plants, but the truth of the matter is that tunneling mammals have their roles to play in nature. They introduce all-important organic matter, for one thing.
For those of you who grow edibles, especially produce that commonly graces our tables, you have a sense of humus. This is organic matter that has been consumed and altered by soil fungi and bacteria into large amorphous molecules that tend to resist further decomposition. Humus does break down but it does so very slowly. The introduction of too much oxygen through tillage burns up organic matter quickly and most of the nutrient value is lost. If you’re a gardener, why would you want to engage in a practice that is counterproductive and against your own interests?
Urban/Suburban Ecoliteracy 