Wednesday, July 22, 2009

Building and Feeding Healthy Soil, Part One of Four

All gardeners know healthy plants start with healthy soil, but not all gardeners know everything it takes to really make the soil healthy. I certainly don’t, but here’s a start. If you ask that question, most gardeners will say “compost”, sometimes without understanding exactly everything compost really does in the soil, other than loosen the soil and probably add some fertilizer.

But, oh my, healthy soil is so much more than just dirt with lots of compost! If your soil has any organic material in it, you probably see a few earthworms when you dig. You might also see a few other critters like centipedes, larvae, and who knows what else… but the vitally important ‘work-horse” life that builds and maintains healthy soil is seldom seen unless you have a microscope. These small critters (microorganisms) are bacteria, mites, nematodes, fungi, yeasts, molds, protozoa... and they are present in soils in astounding numbers!

The top several inches in a square foot of good garden soil may hold 50 earthworms, but a mere teaspoon of good, healthy soil may contain a billion bacteria, several thousand protozoa, a few dozen nematodes and many yards of almost invisible fungal hyphae (thread-like filaments). All living things, including soil organisms, must eat to survive. If soil organisms have the right things to eat, they make healthy soil, which feeds the plants, which then feed us.

What do these critters eat? Well, some eat chemicals like sulfur and nitrogen, and others eat things containing carbon… such as organic plant material (wood chips, leaves, green manure, and compost), waste products from other organisms (microscopic size to very large sizes like a horse), and sometimes they eat each other.

Now, here’s a catch… (isn’t there always a catch?). If we feed a human being a diet consisting solely of hamburgers, fries and sodas, they will live, and will have some energy. But sooner or later, their vitality will wane because they haven’t consumed a well-balanced diet containing ALL the nutrients needed for building and maintaining full health. Plus, you cannot feed a human just every now and then and still expect healthy vitality. The same is true for soil life. They need a constant supply of good nutrients in balance, and just adding compost and NPK doesn’t cut it.

By a neat action of Grand Design, plants provide much of the food the critters need. Plants do this through photosynthesis, producing energy in the leaves. This energy is converted to chemicals the plants give off in their root area (which is called the rhizosphere and is the tiny space immediately surrounding the roots). These chemicals are mostly carbs (which include sugars such as glucose and sucrose), amino acids, proteins, water and minerals, which attract and feed beneficial microbes.

The other neat action of Grand Design is that the waste products given off by the soil organisms are the very things the plants need (and in the right form to take up by the roots)… nutrients like minerals, vitamins, and nitrogen. For an example: plants may not be able to take up phosphate ions that are locked up in soils. The mycelium (the thread-like part) of the mycorrhizal fungus can process the phosphorus and make it available to the plants. (Mycorrhizae are especially beneficial for their plant partner in nutrient-poor soils.) Some microbes are able to “fix” nitrogen from the air and make it available to plants. These are often bacteria, blue-green algae and mycorrhizae/

Stay tuned for Part Two, coming soon.

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