How many microbes? Consider these facts from the U.S. Department of Agriculture’s Natural Resources Conservation Service:
— One cup of soil can hold more bacteria than there are people on Earth.
— 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, 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. “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 – especially in areas with clay soil — developed their own issues. They got waterlogged.
“The most important thing to do when your soil is wet is nothing,” Zien said. “Walking on or working a wet soil causes compaction, making it difficult for water, fertilizer, air, beneficial soil biology and roots to move through and function in the soil.”
BUILD BETTER SOIL
Your soil is alive and teeming with microorganisms. Plants need these microbes to break down nutrients.
— Feed the soil, not the plants. Microbes eat organic material such as dead leaves, compost, worm castings and manure. In turn, they process this food into water-soluble nutrients that plants absorb through their roots.
— Microbes need to breathe. To operate efficiently, microbes require tiny pockets of air in soil. If the ground is constantly saturated, they drown. Anaerobic (bad) bacteria, which can survive without air, take over and produce alcohol – and plant roots rot.
— Soil has structure; don’t rip it up. Repeated tilling and churning collapses the soil structure, contributing to the formation of hardpan, an impenetrable layer of clay. By treating soil with tenderness, air pockets are not disturbed. Instead, layer organic material on top; microbes will come up to get it.
— Soil has texture. That texture comes from the mix of gritty sand, smooth silt and sticky clay. Knowing how much of each ingredient is the key to understanding how that soil will perform.
— Test your soil before adding amendments. Know your soil’s pH — its acidity or alkalinity. Inexpensive pH test kits are available at nurseries and home-improvement centers. The lower the number, the more acidic the soil; higher numbers are more alkaline. Most plants prefer “neutral” soil — 6.5 to 7.0 on the pH scale. Acid-loving plants such as camellias and azaleas prefer a pH of 5.0 to 6.0. Never go to extremes on the scale. Other basic soil tests measure macronutrients — nitrogen, phosphate and potassium — that are the primary building blocks for plant growth. More extensive testing will measure secondary nutrients — calcium, magnesium and sulfur — and micronutrients including iron, copper, boron and zinc. These other nutrients act like vitamins for plants, promoting health and strong growth, but too much can be fatal.
— Building good soil takes time. Don’t expect overnight results. When making adjustments, take baby steps.