Diane Miessler: Cover that dirt!
July 13, 2018
As a soil food web enthusiast from way back, I hate to see any dirt exposed to air and sun, knowing as I do how our soil food web friends love shade and moisture. Under ideal circumstances, the soil food web — worms, germs, protozoa, bugs and other creatures of the underworld — will create rich soil and all the nutrients your plants need.
Mulch is one way to protect the life in your soil. Another, even more effective approach is the use of cover crops. That's because — are you sitting down? — Plants improve the soil!
Ever pull up a clump of grass from a stretch of sandy, bare soil and noticed the dark soil clinging to its roots? The roots of that grass created its own rich dirt, by attracting microbes for that purpose.
All plants pull nourishment from sun and air, turning carbon dioxide (CO2) and water (H2O) into carbohydrates (CHO, get it?). Some of those sugary carbs are used to build plant structure and to make strawberries delicious, but some are "sweated" out of the roots as sugary exudates.
Those sweet exudates attract microbes to the root zone, where they dine on the sugars while breaking down minerals in the soil into forms the plant roots can use. This little party in the root zone has the happy side effect of creating humus, which is just a long chain of carbon that happens to create shelter for water, air, microbes and nutrients.
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As each microbe eats and/or is eaten by something else, it tacks carbon atoms onto an ever-lengthening chain in sort of a carbon bunny hop. That chain then becomes humus, a very stable form of organic matter that is pretty much done rotting. Humus creates a spongy, moist home with lots of electrical charges that hold onto nutrients that would otherwise be washed away by rain or watering.
Roots seem designed to enrich soil for the plant they support. Different plants need different mixes of nutrients; roots attract and create a custom mix for their particular plant. So the more, and more diverse, plants there are growing in soil (given adequate water), the richer it will become.
Protecting your plants
Which leads us to cover crops. These are plants you grow with the express purpose of improving the soil. Cover crops can include grasses, legumes, and non-leguminous broadleaf plants like, for instance, buckwheat and Daikon radish, a couple of my personal favorites.
There are lots of ways to use cover crops. A common one is to plant them in late fall or early spring, then till them in (if you till, which I don't — see previous diatribe on the topic). Another is to pull or mow them and lay them on the soil as mulch. And yet another is to just let them grow alongside your crops; this is my current approach.
I have areas I've mulched with alfalfa hay and planted into, and I have places where I seeded my favorite mixture of cover crops: buckwheat (for lots of organic matter and for bee forage), forage/Daikon radish (because it grows deep roots that break up my hard clay soil), Anasazi beans and soybeans (because they pull nitrogen from the atmosphere and fix it in the soil, and because I can eat them).
Seedlings vs. seeds
What I'm noticing is that the soil where I've planted tomatoes and peppers right amidst the cover crops is more moist than the places where I've pulled up the cover crops and let them lie as dry mulch. The live plants seem to collect what water they get and hold it in the soil. Dry mulch protects the ground from sun and drying air but, unless water is pretty copious, it seems to catch and then evaporate the water.
What I've begun to do, then, is just flatten the live cover crops around my cultivated plants, to allow sun and water from my sprinklers to reach them. This works when planting seedlings versus seeds.
For seeds, I pull up a handful of cover crop where I want to plant, shake off the rich dirt, seed that area, and lay the pulled-up cover crop loosely over the seedbed to shade the soil. I use organic snail bait, as I haven't found another way to manage them in the slug-haven I've created.
Cover crop seeds can be purchased at Peaceful Valley or as bulk beans at Briar Patch, and can be planted any time of year, with or between crops.
Diane Miessler is a nurse, science buff, permaculture designer, and compost goddess. Her book, "An Aging Hippie Chick's Guide to Worms, Germs, Beautiful Gardens," and "Afternoon Naps: How to Have a Sustainable Garden Without Making the Neighbors Hate You," will be published later this year. Contact her via her website at aginghippiechickgardening.com.