Wednesday, July 29, 2009

Building and Feeding Healthy Soil, Part Two

One of the primary roles of microorganisms in soil is to decompose organic compounds so the plants can utilize them. In fact, most of the nutrient (fertilizing) components we apply to our gardens cannot be used by plants as is, straight out of the bag or the compost pile. It’s the teeny-tiny soil organisms that do the real ‘conversion’ work!

The relationship between plants and microbes is called symbosis (
"the living together of unlike organisms"). A symbiotic relationship may be categorized as being mutualistic (both benefit), parasitic (one benefits, one suffers), or commensal (one benefits, no gain or loss for the other). In the case of the mycorrhizae, their symbiotic relationship with plants is mutualistic (both benefit).

As discussed in Part One, plants make energy via photosynthesis; they then chemically convert that energy into food at the root zone for microbes. Mychorrhizae, in their mutualistic symbiotic relationship with plants, “fix” nitrogen, which the plants use for growth. Different soil microorganisms digest and convert other nutrients necessary for healthy plants.

So, how do you get a good soil organism start in your garden if it is barren? Microorganisms are everywhere… on plants, in the dirt, in the air and on our skin. Soil organisms are rarely completely killed off, but in poor soil they dwindle, become dormant and unproductive. You can ‘awaken’ these dormant organisms with food, and you can add new soil organisms several ways including incorporating green manure and compost (which contain both living organisms and a food supply). If you plant a legume cover crop and incorporate it into the soil when it matures, it will add both food, and the organisms living on and in it.

Products like worm castings add some soil organisms, although they add more in the way of food. Some of the expensive liquid products contain live cultures. Just remember, you must feed the soil organisms, especially if there are no or few plants to feed them. (Seedlings don’t count; they are too small to give off any food in their roots.)

What do you feed the soil organisms? Many folks use a manure or compost tea with added molasses to supply the sugars to jump-start the soil organisms. Some make their own EM tea (search for Efficient Microbe information online). Teas can be used as a foliar spray or a drench, but foliar sprays are faster-acting. Compost and green manures add carbon-based foods.

Another benefit of adding compost is that it creates small air pockets in the soil, and beneficial (aerobic) organisms need oxygen as well as food, provided in a moist (but not saturated) soil. As the soil organisms break down compost for food, it becomes humus. Humus provides tilth, breaking up compaction.

You need to also feed the microorganisms some minerals. Most cultivated soils tend to be deficient in minerals (including trace minerals), because the minerals have been taken up by plants and not replaced. Applying fertilizers like NPK doesn’t add a full spectrum of minerals back into the soil, and may be adding too much nitrogen that soon becomes run-off. Soil organisms need trace minerals along with food and oxygen to grow and multiply.

With a good, balanced food supply, one bacterium is capable of producing 16 million more in just 24 hours. (They simply divide, providing conditions are favorable.)

Stay tuned for Part Three, coming soon.

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