Mikl Brawner, co-owner of Harlequin’s Gardens in Boulder, offers these ideas to improve soil health.
➊ Minimize soil disturbance, like plowing, tilling and overgrazing. When soil is turned, the fungal networks are broken and carbon is exposed to oxygen, which is then oxidized and returned to the atmosphere as carbon dioxide. Research shows that in the last century, we have burned up 90 percent of the organic matter in our soils. It’s now recognized that carbon is the key driver of the nutrient-microbial recycling system.
➋ Keep the soil covered with mulch, plants or cover crops. Mulch can be shredded leaves and wood chips, or any plant residue without seeds. Cover crops reduce wind and water erosion, and evaporation. They also moderate soil temperature, provide habitat and supply a slow release of nutrients—all of which makes microbial soil life more successful.
➌ Plant diversity creates complex microbial populations as well, increasing soil resilience through improved rainfall infiltration, nutrient cycling, and reduced diseases and pests.
➍ We use mycorrhizae—a beneficial fungi inoculation—whenever we plant. It’s proved to be very beneficial in getting plants established, especially in drier conditions. We also add mycorrhizae to potting mixes.
➎ Even in the off-season, when we let gardens go fallow, we still need to feed soil microbes. In vegetable gardens, this is usually accomplished through cover crops that also add nitrogen and organic matter to the soil when they are cut down. Evergreen perennials and shrubs also feed microbes in winter.
➏ Worm castings are a great source of plant-available nutrients. Rock dust and seaweed are good sources of micronutrients that are so essential for plant health. Humate is a mined carbon concentrate that benefits microbes’ ability to make soil nutrients plant-available.
➐ Expanded shale is a great clay buster that doesn’t break down and supports microorganisms and good soil structure.
➑ We use organic fertilizers made from fish, seaweed and animal manure, along with alfalfa, rock dust and humate. We use granular formulas for longer-lasting effects and liquid fertilizers for foliar and faster-acting effects. For young veggie plants, we use compost tea mixed with a liquid fertilizer. But we err on the side of underfeeding rather than overfertilizing.