Building Fertile Soil

Doreen G. Howard discusses the basis for building fertile soil for the garden, including information on no-till soil and permanent beds, mulch and cover crops.

| June/July 2003

Building fertile soil means learning how to feed the soil to feed the plants.

It's a fundamental axiom of organic gardening and farming, and once you understand what "feeding the soil" means to building fertile soil, you'll also understand why organic methods, and no-till techniques in particular, work so well.

Even though you can't see most of it, a complex soil food web lives in your garden; it's teeming with earthworms, mites, bacteria, fungi — all kinds of mostly microscopic, interdependent organisms that release mineral nutrients and create the loose soil structure crops need to thrive. Beneficial mycorrhizal fungi (see "The Magic of Mycorrhizal Fungi," page 24 in this issue) grow in and around plant roots, mining subsoil for nutrients and water to share with your crops. Other microorganisms prevent diseases and help plants withstand insect attacks.

Your crops actually help feed all this underground life. Ray Weil, a renowned soil scientist at the University of Maryland, College Park, says that while plants invest a "substantial amount of their photosynthesis in feeding soil microbes, the plants are obviously getting benefits back."

Think of plants, with their green chlorophyll, as little solar-powered engines that pipe a steady flow of carbohydrates out through their root hairs. Between 20 percent and 40 percent of a plant's total carbohydrate production is released into the soil through its roots. In the nutrient-rich area around the root hairs, microscopic bacteria and fungi feed and multiply. Nematodes (tiny worms) and other critters move in to feed on the bacteria; in turn, the root hairs absorb nutrients released by the concentration of microbes.

But this complex, mostly invisible soil ecosystem can be damaged easily. Chemical fertilizers, dehydrated chicken manure or high-nitrogen blood meal can burn tender root hairs, and tilling or plowing destroys soil texture, disturbing the layered web. Leaving the soil bare shuts off the carbohydrate food supply; lack of moisture and ultraviolet rays kill some of the organisms that dwell in the surface layer. (Mother Nature almost never leaves the soil uncovered; only on farms and in gardens do we see naked soil.)

2/9/2009 10:19:00 PM

I have been research soil for the last month or so(spring will come)for ways to create a more fertile soil. I read through a number of good sites and did learn a lot about soil that confirmed what I already knew ie the typical system of adding various materials to your existing soil followed by DIGGING IN. I have followed that process in the past with intermittent success. So I was very excited when I found your EXCELLENT site discussing the pros of using cover crops to sustain the fertility of soil and the process of building a new garden on top of the existing one without digging the new and old beds together. I need look no further THANK YOU FOR THIS FREE INFORMATION I can hardly wait for spring! I do remember my mother rotating her garden to use the nitrogen enriched soil created from her pea crops..... Val Stirling

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