By Mark Shepard
This is an excerpt from the book Water for Any Farm by Mark Shepard and published by Acres U.S.A. Reprinted with permission from the publisher.
The obvious result of keyline design on any property is water capture via excavated channels. Not so obvious is increased water infiltration through strategic use of a subsoiler and through the increase of soil organic matter. This increase in soil organic matter would come not from additions of compost but from the extensive sowing of perennial plants, especially grasses. Although water for growth of crops was my primary goal, I learned over time that water is also the “key” to building soil. I learned through experience what Yeomans had claimed in Water for Every Farm. Early in the book, page two in fact, he stated:
The cultivation, irrigation and stock management techniques, of Keyline are used to greatly speed up the natural process of living soil formation. Conversion of subsoil into topsoil may, under natural conditions, occur at 10 to 15 tonnes per hectare each year. On Keyline farms this figure has been increased to 10 to 15 hundred tonnes per hectare per year during the conversion process, which usually takes two or three years. The numbers may be startling but this result is achieved by deepening the topsoil by 10 to 15cm (i.e. 4 to 6 inches). Deepening the living top soil to 30 to 45 cm (twelve to 18 inches) is a practical short term goal.
Most of us have been told that it takes geological eons for topsoil to form. Since plant and animal life can only produce minute amounts of topsoil per year, the addition of composts is considered the only way to really increase a land’s topsoil over time. What I have experienced in the past twenty years, however, was not the addition of topsoil from the top, but the conversion of subsoil into topsoil. We converted farmed-out, red clay subsoil into dark, almost black topsoil. These same principles hold true for converting sandy or gravelly subsoil into topsoil.
Converting subsoil into topsoil involves a simple set of practices that interact in an infinitely complex manner. To convert subsoil into topsoil, all that one needs to do is improve the conditions for life in the soil.
Life in the soil is myriad and diverse. Everything from fungi and bacteria to nematodes, thrips, springtails, insect larvae, beetles, mollusks (snails and slugs), sowbugs, earthworms, amphibians, mammals, and an unknown number of additional species contributes to the creation of active, living topsoil. In order for soil life to flourish, these organisms need air, water and food. Simple!
Air in Soil
Air is introduced into the soil in several ways. Naturally air enters into the soil through the pore spaces between granules of soil. Sandy soil has larger pore spaces, so air can enter it more easily. Clay soils have smaller pore spaces between particles, which makes it more difficult for air to enter the soil. Earthworms, dung beetles, moles, birds, ground squirrels, and other burrowing creatures large and small create holes in the soil, which allow air to enter. Plant roots, especially the fibrous roots of perennial plants, allow air into the soil by mechanical tunneling and most obviously when they die and decay.
Water in Soil
Arguably the single most significant soil-building piece of farm equipment in the keyline toolbox is the subsoiler. Subsoiler, ripper, deep-tine ripper, mole plow, and Yeomans plow are all names that I’ve heard farmers call this non-inverting soil-loosening tool. In its simplest form, it’s a steel hook dragged through the ground. It is designed to cut into the soil and slightly lift and shatter the soil on either side of the tool. In it most complex forms, the Yeomans plow includes features such as cutting coulters, vibrating shanks, multiple shanks, specialized toolheads for various lifting and shattering actions, rollers to crumble and slightly flatten the small linear scar left by the tool, seed hoppers, and liquid applicators for fertilizers or biological inoculation.
Whichever subsoiler you use is entirely up to you and depends on your traction equipment, your budget, and the specifics of your farm.
ABOUT THE AUTHOR:
Mark Shepard heads Forest Agriculture Enterprises and runs New Forest Farm, an 106-acre commercial-scale perennial agricultural ecosystem that was converted from a row-crop grain farm. Trained in mechanical engineering and ecology, Mark has combined these two passions to develop equipment and processes for the cultivation, harvesting and processing of forest-derived agricultural products for human foods and biofuel production. Mark is a certified permaculture designer and teaches agroforestry and permaculture around the world. He is a frequent instructor at the Acres U.S.A. Eco-Ag Conference & Trade Show. (LINK to ecoag.acresusa.com)