Issue link: http://winesandvines.uberflip.com/i/998810
BOOK EXCERPT July 2018 WINES&VINES 55 crops have access to nitrogen through the fertilizer, elements that microbes previously converted into usable forms may remain inac- cessible when the right soil organisms are not around to do their job. When plants get all the macronutrients they need for free from fertil- izers, they shut off their expensive exudate faucet, denying the microbes that are left in the rhizosphere a much-needed food source. This turns crops into botanical couch potatoes and helps make degraded farmland dependent on nitrogen fertilizers. It also means that while plants may get certain major elements they need to grow, they lose out on the microbial allies that help procure the mineral micronu- trients they need to be healthy and mount a robust defense against pests and pathogens. More than one-half century after Sir Albert Howard first proposed his Law of Return, we finally understand how it works. There is a biological basis for the central role soil organic matter plays in growing healthy crops and sustaining bountiful harvests. Fertility isn't only about chemistry and physics. Soil ecology and nutrient cycling driven by microbial life also matter. Even when standard soil chemistry tests say you need to add fertilizers, the right soil life — if present and abundant — may be able to supply what plants need. Growing evidence shows that synthetic fertilizers work like agricultural steroids, prop- ping up short-term crop yields at the expense of long-term fertility and soil health. Consider fertilizers and agrochemicals as like antibiotics — a godsend if you really need them, but fool- ish to rely on for regular use. And this, of course, is exactly what we've been doing for decades. In hindsight, we know that our dependence on the plow and fertilizers to pump-up crop yields depleted soil organic matter and dis- rupted the beneficial fungi that extract crucial micronutrients from rocks and deliver them to crops. When we take out mycorrhizal fungi — eliminating or limiting their role in nutrient acquisition — and compromise microbial roles in pest and pathogen control, we have to re- place them with fertilizers and pesticides. But we can reverse this by cultivating ben- eficial microbial life. The key to doing this seems to be practices that build soil organic matter — feed them and they will come. Farm- ing practices that maintain high levels of soil organic matter support the diversity of benefi- cial soil life that in turn supports plant health. Organic-matter rich soils promote beneficial soil nematodes over plant-parasitic nematodes as well as bacterial communities that suppress pathogens. And it is well established that they are more fertile. Speaking at farming conferences for the past few years, I met farmers discovering how to rebuild fertile soil. They are showing how highly productive agriculture can cultivate soil fertility, using modern technology to update traditional methods and restore productivity to degraded farmland, while sustaining high yields with decreasing energy and input use. Their experiences challenge the wisdom of currently conventional agronomic practices and prove that farming practices that build soil health can reverse trends millennia in the making. The key to maintaining soil health lies in the world of soil life, in the microbial cycling and recycling of nutrients from mineral and organic matter. Herein lies the good news. For the short lifespan of microbial life means that restoring life and fertility to the soil—and in- creasing the productivity of marginal farms — is not only possible, but can happen faster than we ever imagined. David R. Montgomery is a professor of Geomorphology in Department of Earth and Space Sciences, University of Washington, and author of Dirt: The Erosion of Civi- lizations and Growing a Revolution: Bringing Our Soil Back to Life, and co-author of The Hidden Half of Na- ture: The Microbial Roots of Life and Health. Connect with him at Dig2Grow.com or on Twitter (@Dig2Grow).