How to build better soil? Stop treating it like dirt

A single spadeful of rich garden soil contains more living species than can be found above ground in the entire Amazon rainforest.

If you packed all the microbes from an acre of land together, they would weigh as much as two cows.

“We know more about things a billion light years away than about what’s happening 6 inches under our feet, ” said Zien, founder of Living Resources Co. in Sacramento, California, which provides soil and organic gardening consulting.

Microbes play a vital role in soil health.

“Good, healthy soil is alive with beneficial soil organisms known as the soil food web,” Zien said. “These organisms create soil structure, improving drainage and aeration. Nutrients and moisture are stored by the soil biology that makes them available to plant roots, minimizing the need for fertilizer and irrigation. They also provide plant growth hormones and fight off pests, allowing your plants to grow healthy, pest-resistant and drought-tolerant.”

Years of drought severely stressed our soils — and microbes.

“Our soils are scorched,” said Gisele Schoniger of Kellogg Garden Products in Carson, California. “They need replenishment more than fertilizer.”

As Kellogg’s longtime organic gardening educator, Schoniger teaches gardeners throughout the West how to take better care of their soil.

The lack of water actually can change soil’s acidity (or pH) level.

“The less water, the higher the pH and the more alkaline your soil becomes,” she said. “The more water, the lower the pH. Organic matter helps stabilize pH and keep it in the right zone, the neutral zone (in the middle of the pH scale). If the pH is too high or too low, plants can’t use all the nutrients (available in the soil). … Organic matter stabilizes the pH and holds it there.”

Organic matter — compost, manure, shredded bark, rice hulls, coconut fiber, peat moss, kelp, bone meal and other natural amendments — does more than keep pH in balance. It feeds those microbes.

“Organic matter is the fuel that makes the whole system work,” she said. “If you do nothing else, put down organic material around your garden.”

Organic matter also helps soil absorb and store water. After recent winter storms, some landscapes developed their own issues. They got waterlogged.

“Wait until the soil dries out a little and top-dress with worm castings,” Zien said. “The soil biology it contains will move into the soil with subsequent rains. These critters will create soil structure that will open up poorly draining clay soils, improving drainage and aeration.

“In spring, when the soil dries out a bit more, aerate the soil. Follow that with an application of an organic fertilizer, more earthworm castings and compost. Avoid tilling your soil — that actually causes soil compaction.”

Those worm castings have an added benefit, Schoniger said. They fight whiteflies and other garden pests.

Sprinkle the castings in a circle around the plant (at the dripline of trees or shrubs), then cover with mulch and let the castings work down into the soil.

Besides being rich in nutrients, worm castings contain a substance that naturally breaks down insect skeletons, she said. But water will bead up on pure castings; they need a little mulch on top to do their garden magic.

“Worm castings are the best value you can get for your garden,” she said. “A whitefly won’t go near a plant that could break its body down.”