Marin IJ Articles
April 6, 2019
Want fabulous plants? You need healthy soil. Whether you’re growing edibles, flowers, a lawn or trees, healthy soil is a must. Not only will plants look and grow better, they’ll be less susceptible to pests and diseases.
Vibrant, healthy soil is loose, friable, well-drained and rich in organic matter. It’s generally about 45 percent minerals, 25 percent air, 25 percent water and 5 percent organic material. And it’s the organic component, supporting a nearly invisible living ecosystem, that can transform ordinary soil into the stuff of gardener’s dreams.
Way back in the 15th century, Leonardo da Vinci observed, “We know more about the movement of celestial bodies than about the soil underfoot.” Times haven’t changed much.
What you see going on with your plants above ground is largely determined by what goes on beneath your feet, mostly in the top 4 to 8 inches of soil. In its natural state, soil is a living environment, teeming with biological activity.
“Countless small, retiring inhabitants carry out their indispensable business in the soil,” says James Nardi in his book, “Life in the Soil.” Referring to creatures that aid in decomposing materials, he continues, “They happen to be the recyclers that can produce that key organic ingredient of healthy soil known as humus.” That’s the stable organic matter that remains after dead or dying materials have been completely decomposed.
There are three levels of organisms active in the soil. First are the bacteria and fungi that break down organic matter. They hold nutrients in their body, and when they die, they become slow-release fertilizer for plants. They’re also food for the next level — small predators like nematodes and protozoa. The third level, higher-level predators like millipedes and earthworms, keep the second level in check. Damage to any part of this delicate balance can impact the entire ecosystem.
Managing soil health is mostly about maintaining a suitable environment for the myriad creatures that inhabit it. You can do it with five relatively easy steps: disturb the soil as little as possible, grow a wide array of plant types, keep it covered, add organic matter and minimize the use of chemicals.
• Minimize disturbance: Rototilling is like an earthquake and tornado combined for the creatures living in the soil and can result in a hostile environment. Instead, add organic materials the way nature does — by laying them on the surface. The biological life in the soil will slowly decompose them and release plant nutrients. Let earthworms, Nature’s rototillers, do much of the work!
Tilling may be necessary in some cases — if you’ve got sticky clay or heavily compacted soil. A one-time mixing in of organic matter can aid in creating more workable soil.
• Maintain plant diversity: Many of the substances soil microbes feed on are produced by plants. The greater the variety of plants, the broader, the more diverse the population of soil microorganisms will be.
• Keep it covered: Soil should always be covered by plants, their residue or mulch. Cover conserves moisture, helps moderate temperatures, suppresses weed growth, and provides habitat for soil critters that spend some of their time above ground.
• Add organic material: Any plant or animal material that goes through the decomposition process provides nutrients and habitat to soil microbes, binds soil particles into aggregates and improves the water holding capacity of soil. Compost and animal manures are common choices.
• Minimize the use of chemicals: The fertilizers and pesticides that gardeners use to enhance plant growth may be toxic to microorganisms in the soil, particularly the first level, destroying some, and possibly impacting survivors so that they are no longer beneficial to the soil ecosystem. Adding organic compost rather than synthetic fertilizer and utilizing an integrated pest management approach can help reduce the use of chemicals.
For healthy soil, keep in mind the mantra of soil scientist and educator Stephen Andrews, “compost, compost, compost” and “mulch, mulch, mulch!”