Our understanding of the soil food web has increased rapidly in the 21st century as microscope technology improves and soil biology research continues, and this opens new doors for gardeners and farmers to employ organic solutions for healthier, more vigorous crops. To explain how soil bacteria are irreplaceable in our gardens, my guest this week is gardening columnist and author Jeff Lowenfels.
Jeff has written a weekly garden column for the Alaska dispatch for more than four decades, plus he’s a retired natural resources attorney who earned the title “America’s Dirtiest Lawyer.” He also previously hosted a gardening radio show and Alaska public television’s most popular show, “Alaska Gardens with Jeff Lowenfels.” He’s a former president of the Garden Writers Association of America (now known as GardenComm) and a GWA fellow and Hall of Famer. Jeff’s new book is “Teaming with Bacteria: The Organic Gardener’s Guide to Endophytic Bacteria and the Rhizophagy Cycle,” the fourth volume in his “Teaming” series.
Jeff grew up in Scarsdale, New York, where he planted, weeded, mowed, and picked fruits, flowers, and vegetables on his father’s 8-acre “gentlemen’s farm” until he left for Harvard College in Cambridge, Massachusetts, where he studied geology. He continued his studies in Boston, Massachusetts, at Northeastern University School of Law, earning a Juris Doctor in environmental law.
Jeff is also the founder of Plant a Row for the Hungry, a public service program he began in Anchorage that has since gone national and has resulted in millions of pounds of garden produce being donated to feed the hungry every year. He was a guest on my public television program “Growing a Greener World(r)” during the show’s second season to talk about Grow a Row for the Hungry for an episode all about how gardeners can help people in need.
Jeff is an old friend, though it’s been a long time since we caught up. He was a guest of the “Growing a Greener World with Joe Lamp’l” podcast — the predecessor to “The joe gardener Show” podcast” — way back in 2010 to discuss his book “Teaming with Microbes.” I am a big fan of the book; it’s one of my “Must-Have Books for Every Gardener.” Jeff points out that a lot has changed how we understand the soil food web since “Teaming with Microbes” was first published in 2006. That’s why he continues the “Teaming” series with books on fungi, nutrients, and bacteria.
Before proceeding with my conversation with Jeff about “Teaming with Bacteria,” I want to take a second to remind you that I have a new book released last month. It’s titled “The Vegetable Gardening Book: Your complete guide to Growing an edible organic garden from Seed to Harvest” and can be found online and at local bookstores. It’s chock full of insider tips and new-to-you information that will help you step up your gardening game and tackle challenges.
And on tap for 2023 is my new Online Gardening Academy(tm) premium course, Organic Vegetable Gardening. Sign up for the waitlist here.
What We’ve Learned Since ‘Teaming with Microbes
Between the publication of “Teaming with Microbes” in 2006 and today, soil science has made strides. We knew then that plants take photosynthetic energy and use about 30%, 40%, or even 50% of that energy to produce exudates that drip out of their roots.
“The plant designs the exudates to attract bacteria and fungi,” Jeff explains. These microorganisms, or microbes, eat the exudates, and then nematodes and protozoa come along that eat bacteria and fungi. The waste they excrete is in the form of nutrients that plants can easily absorb through their roots.
“What they poop out turns out to be plant nutrients in usable form,” Jeff says. “In other words, the microbes put a charge on it. And if you read my second book, ‘Teaming with Nutrients,’ you’ll see that that charge is necessary for these things to go inside the plant.”
Years after “Teaming with Microbes” was published, the critical role of mycorrhizal fungi was confirmed. We know that 90% of plants form a symbiotic relationship with mycorrhizae.
“The fungus feeds the plant in return for getting these nutrients,” Jeff says.
The system that he described back in 2006 was a soil-mediated nutrient system. He says the idea is that nutrients went into the soil, and from the ground, they moved into the plant.
The mycorrhizal system that soil scientists later discovered works by nutrients going from the soil into the fungi, and then the fungi trading those nutrients with roots for exudates.
More recently, Jeff says, scientists gained a greater understanding of rhizobia, a nitrogen-fixing bacteria that forms a relationship with legumes. The plant attracts the bacteria, which create a home in a folded-up root hair. As the bacteria reside there, they pull nitrogen from the air for the plant’s benefit.
Not all of the nitrogen stays put.
“Some of it leaks out. Some of it ends up going into the soil,” Jeff says. “And when the plant dies, all of it ends up going into the soil and feeding future generations of plants nitrogen.”
