GARDENING 101: Manufacturing Soil

The Rev. Dana Prom Smith, S.T.D., Ph.D (2/16/09)

The author of such popular phrases as "the medium is the message" and "global village," Marshall McLuhan in Understanding Media wrote that a medium is an "extension of ourselves." A medium could be a hammer, fork, cartoon, rifle, fishing pole, tennis racket, motion picture, or even soil. It's anything by which people extend their ability to affect their environment, empowering themselves to bring about a cascade of changes.

Soil is the gardener's medium. Without it, save for hydroponic gardening, there's no gardening. Soil is the medium through which gardeners extend themselves to affect their environment, and, as such, soil is the gardener's message.

Dirt isn't the same thing as soil. Soil is manufactured by gardeners using sand, silt, clay, and organic matter, in short, enhancing what has been given them. In Flagstaff, we also have limestone, sandstone, and volcanic debris.

The ideal soil consists of 40% silt, 20% clay, and 40% sand in addition to organic matter. Sand is gritty and can be seen with the naked eye. Both silt and clay are finer, so fine that their particles cannot be seen with the naked eye, clay being the finest.

The problem with clay, of which there is an abundance in Flagstaff, is that when it dries, it hardens, so hard that most of the garden plants wither because their roots cannot penetrate the clay. However, it holds moisture well while sand doesn't. Mixing sand with clay loosens the clay while keeping its ability to retain moisture.

Alas, sand is scarce in Flagstaff, but we have a good substitute which may be better than sand. Volcanic cinders are everywhere and are about 2/3 sand and 1/3 geochemical nutrients. Mixing volcanic cinders with clay loosens the clay. Weathering, such as harsh winters, howling winds, and torrential rains, gradually releases the nutrients from the cinders.

Forget about silt which occurs in washes, along stream beds, in certain meadows, on alluvial slopes, and on deltas. It's of no practical value since most of it occurs somewhere downhill from Flagstaff.

The next step to a nascent soil of clay and cinders is adding organic matter. Organic matter is important because it positively affects the mycorrhizae already in soil, making them more effective. Mycorrhizae are fungal middle-men or brokers, transferring nutrients from the soil to the plant's roots. The soil may be loaded with nutrients, but without mycorrhizae they aren't transferred to the roots.

Obviously, the best organic matter is decayed organic matter because the nutrients are in the decay. Also, organic matter aerates the soil as do the cinders. Organic matter turns the clay and cinders mix into what might pass for clay loam. The best kind of soil runs through the fingers. If it clots and doesn't flow, like blood in the arteries on the way to the heart, it ain't so good. Clots, clods, and clumps are signs that the nutrients aren't flowing as well as they should, a gardening mycrocardial infarction.

Digging kitchen scraps (no fat, meat or oil), manure, and decayed pine needles, fallen leaves, clippings, even shredded newspapers, into the soil is good, but compost is better because as the name suggests, it's already decomposed. Compost is simply a pile of organic matter with a 3 to 1 ratio of carbon material to nitrogen material in which the carbon material is broken down by the nitrogen material, releasing the nutrients. Carbon material is often called brown while the nitrogen material is called green, although coffee grounds are green horticulturally if not visually.

Composting is best done in bins and large containers, but our homesteading ancestors did it in piles, usually several paces from the cabin. In a way, the modern composting movement is a return to the past as a way of finding the future in a horticultural time warp.

Compost is the heart of the medium of soil. It's the difference between a garden that thrives and one that withers. Thriving gardens are the message of the medium, a message with a cascade of consequences, beginning with food and beauty and extending all the way to a habitable planet.

Copyright © Dana Prom Smith 2009