A growing number of experienced organic gardeners are coming to the conclusion that after the soil in a garden bed has been improved, the less it is disturbed the better. Apparently there is good reason for this: Microbiologists suggest that the bacteria, protozoa, and other microscopic organisms that give the soil its life tend to settle in certain layers within the soil and don't appreciate having these layers and their accompanying life styles turned upside down.
Imagine, for instance, a tribesman of the Amazon Basin suddenly being uprooted and placed on the high plains of Tibet. He would not function well in his new surroundings, and he might not survive very long. It's the same when the microbe near the surface of the soil is suddenly dumped a foot or more deep and vice versa. The less these organisms, including the more visible earthworms, are disturbed, the better able they are to do their job in keeping the soil healthy and productive. Studies suggest that while bacteria recover after an initial mixing, they tend to lose their vitality with repeated digging, which also damages the soil's crumb structure.
If your soil is poor to start with, then obviously quantities of compost, manure, leaves, straw, and other soil amendments must be dug or tilled in right at the start. Thereafter it pays to be ``gentle with your soil.'' That means: Don't fork it over too vigorously and never rototill it deeply.
Some gardeners even follow a no-dig policy altogether. One famous garden in England -- at Arkley Manor on the outskirts of London -- has not been dug over for more than two decades, though sometimes a seedbed is made by tilling only the top two inches of the soil. The beds are maintained by spreading an inch of well-rotted compost on the surface of the soil each year. This is steadily incorporated into the soil by the action of earthworms and other soil organisms. Rain falling on this compost mulch carries the soluble nutrients down to the plant roots.
A vast majority of these ``soil gentle'' gardeners, however, do undertake some digging and have found the right tool to do so. It is one that fluffs up the soil and allows air to penetrate but does not invert any of the soil layers. The origins of the two-handled fork -- called variously the U-bar, the double-digger, or the bio-fork -- go back to the immensely productive intensive market gardens that surrounded Paris a hundred years ago.
Dr. David Tresemer of the research organization By Hand and Foot, in Brattleboro, Vt., found that the two-handled fork began as a wide and heavy two-tined fork, or pelleversoir, as it was called, generally used by three men in unison. It had long a long handle, giving the users plenty of leverage in heavy soils. ``With a spade,'' says Dr. Tresemer, ``one person could prepare 15 square meters [18 square yards] an hour. With the pelleversoir a team of three could prepare 90 meters an hour. So great was this advantage that small tenant farmers were able to increase their productivity enough to purchase the small farms they worked.'' By the end of the 19th century the entire social structure of France had changed through the tremendous increase in the number of owner-operated small holdings, ``owing in part to this tool,'' Dr. Tresemer says.
Earlier this century, the French engineer Andr'e Grelin decided to combine three pelleversoirs into one wide fork with two handles so that one man on his own could become impressively productive in the garden. Modern steels meant it was possible to produce a tool that was strong yet light enough for one man to handle. Grelin made what might be termed the first modern U-bar in 1948, which he named the Grelinette.
Recently further adaptations have sprung up in the United States, Canada, and Europe, all based on the Grelin tool. There are four that I know of available in the US, one a particularly heavy (30 pounds) and wide tool. The others are about 181/2 inches wide and weigh between 8 and 10 pounds, but have varying handle lengths. Remember, longer handles increase leverage and make it easier to dig without bending.
After pressing the U-bar into the soil, the gardener pulls back on the handles. As the tines rise in the soil they loosen it without inverting the layers. In many respects it compares to the chisel plow in farming, which breaks up the soil without turning it the way the old moldboard plow does.
Another advantage of this type of fork is its ability to work spring soils too wet for conventional spading implements.
To the best of my knowledge these new-old forks are available in the US only from Ecology Action of the Midpeninsula, 2225 El Camino Real, Palo Alto, Calif. 94306 (suppliers of the ultralarge fork); Gardener's Supply, 133 Elm Street, Winooski, Vt. 05404; Green River Tools, 5 Cotton Mill Hill, PO Box 1919, Brattleboro, Vt. 05301; and Smith & Hawken, 25 Corte Madera, Mill Valley, Calif. 94941.