Endomycorrhizal fungi spores are ready to grow into plant roots, carrying nutrients and moisture. Photo courtesy of Jeff Lowenfels.
Published May 7, 2017, in the Wyoming Tribune Eagle, “Soil microbes, no rototilling key to next generation of gardening”
By Barb Gorges
Twice in the space of a month this spring I heard rototilling renounced for the sake of keeping soil microbes healthy.
One speaker was Jeff Lowenfels, garden columnist and author from Alaska who spoke at the Cheyenne Botanic Gardens/Laramie County Master Gardener spring lecture series. The other was Ron Godin, recently retired extension agronomist in western Colorado, speaking at the Wild West Gardening Conference in Cheyenne.
There are a billion microbes in a teaspoon of healthy soil. The interactions of the whole community of microbes is a giant web of who eats whom and who feeds whom.
Basically, decaying plant material feeds microbes and in turn, microbe “excrement” feeds plant roots.
Microbes include nematodes, bacteria, fungi and protozoa. There are some bad actors, but in general, everything balances and plants grow. For example, prairies and forests have self-sustaining soil microbial communities—no synthetic, chemical fertilizers or pesticides are required.
But when European farmers landed in the New World, they opened things up with the plow and have continued to plow ever since. Regular plowing (or hoeing or rototilling) disrupts the soil microbes. They can’t do their jobs. Farmers repaired damage somewhat with applications of manure and compost. But then came the 20th century’s inventive use of nerve gas left over from World War I as insecticide, and leftover nitrogen-based bomb-making materials from World War II became the perfect fertilizer.
Except that it wasn’t healthy for the microbes.
Ectomycorrhizal fungi grow close to the surface of roots and grow webs around them carrying water and nutrients. Photo courtesy of Jeff Lowenfels.
Synthetic fertilizers starve the microbes in a way and pesticides kill off beneficial organisms, causing the need for a never-ending cycle of synthetic fertilizer and pesticide application. This was great if you owned stock in the large chemical companies, but bad when you understand the side effects including health issues animals and humans—especially farmers, because the chemicals get into drinking water and food.
Lowenfels happily dispensed advice on garden chemicals for years until someone sent him two electron microscope photos, one of a fungus that had trapped a root-eating nematode, and the other of a nematode happily chomping a tomato root unimpeded.
In the first photo, the plant was secreting a substance that attracted the fungus, which in turn attacked the nematode. In the second photo, the fungus was missing due to the use of synthetic fertilizers and pesticides.
After his conversion, Lowenfels wrote three books. He said the essential one is “Teaming with Microbes, The Organic Gardener’s Guide to the Soil Food Web,” coauthored with Wayne Lewis. You’ll notice the play on words in the title–healthy soil is teeming with microbes, and you’ll be teaming with them.
Put away the rototiller
First, put away your rototiller. It’s still handy if you are turning your lawn into a pollinator garden, but otherwise, annual rototilling is detrimental to the soil microbe community. Godin said this advice translates to farming as well.
It will take time to undo the cultural tradition of breaking soil down into a fine, clump-less and smooth expanse of dirt. But there are two reasons for disturbing the soil as little as possible, even in a vegetable garden.
First, every time you dig into soil, you bring up weed seeds, most of which require light to germinate. You just made more work for yourself. Cut weeds off at the soil surface rather than digging them.
Second, microbes feeding your plants and fending off bad stuff can’t function if you break them up. Keeping them intact means less work for you, less fertilizer spreading, less watering since healthy soil holds water better. Pesticides are a last resort for serious problems. Re-inoculate your soil with microbes soon after.
In windy Cheyenne, there’s also a third benefit to not tilling your soil into fine dust: microbes “glue” things together and the resulting clumpy soil doesn’t blow away.
In this electron microscopic view, Glomalin, stained green and coated with spores, is produced by a group of common soil fungi. It coats soil particles like super glue, sticking them together in clumps. Photo courtesy of Jeff Lowenfels.
To plant seeds or transplants, make an opening just large enough. The roots will find their way without the soil being “fluffed.” Healthy soil has lots of air spaces already. Then mulch.
Godin’s rule is 100 percent cover, 100 percent of the time. Cover for large gardens or farms could be annual cover crops later mowed to form mulch. In small gardens use leaves, grass clippings and compost.
Replace chemical fertilizers
In the years chemical fertilizers have been around, studies show fruits and vegetables have dropped in nutritional value. It’s due to the missing micronutrients soil microbes used to pull from decomposing plant material and mineral soils. Synthetic fertilizer is incomplete.
Traditional organic gardening recommends digging compost into the soil, but Lowenfels says digging breaks up the soil community. Better to side-dress plants, leaving the compost (or mulch) on the soil surface where microbes will get at it and break it down. It works on the prairie and in the forest—there’s no 100-year-old pile of dead grass, leaves or pine needles.
Lowenfels said there are three different groups of plants in your yard. Perennial flowers, shrubs and trees want their nitrogen in the form provided by fungally dominated soils. The compost that promotes this is the brown stuff (mixed with a little green): dry leaves, bark, wood chips, twigs, branches—like the forest floor.
Annuals, including vegetables, prefer their nitrogen produced by bacterially dominated soil. This is green stuff (with a little brown), grass clippings, freshly picked weeds (without seeds) and fruit and vegetable kitchen scraps.
The prairie, like your lawn, falls in between. It appreciates finely shredded brown fall leaves and thin layers of green grass clippings.
Brew compost tea
Compost tea, compost soaked in water, is another way to inoculate your garden with microbes and feed them too. If compost and compost tea smell ugly, that’s anaerobic activity. You need aerobic activity—more air.
Lowenfels gives directions for making a bucket into “a simple actively aerated compost tea brewer using aquarium pumps and air stones.” Fertilizing your plants, and yes, your houseplants too, is as easy as watering them.
While chemical companies made their fortunes keeping our soils addicted to their products, new companies are offering to aid us in bringing our soils back to health. They are building better compost tea brewers. Labs can estimate your microbe population. Our local independent garden centers will sell you mycorrhizal fungi in powdered form you mix with water.
This new era of catering to microbes has gone mainstream. Lowenfels reported that at the 2016 Garden Writers of America conference, none of the tradeshow vendors was pushing synthetic fertilizers or pesticides.
For the last 35 years, my husband, Mark, and I have cared for our lawn and garden without a rototiller or synthetic fertilizers and pesticides. We mulch the garden and use natural lawn fertilizers. I look forward to adapting Lowenfels’ ideas to step it up.
[If you are also adapting to the new era in gardening, let me know how it is going. Contact me at bgorges2 at gmail.com.]
More information:
Besides “Teaming with Microbes,” his first book, Lowenfels has also authored:
–“Teaming with Nutrients, The Organic Gardener’s Guide to Optimizing Plant Nutrition”
–“Teaming with Fungi, The Organic Grower’s Guide to Mycorrhizae.”
Cheyenne Garden Gossip 