GARDENS : In Good Tilth : How the Biodynamic French Intensive Method Can Improve the Condition of Your Soil
CENTRAL TO the Biodynamic French Intensive method of gardening is a mandate to nurture diverse ecosystems and amplify the forces of nature. Flowers, vegetables, fruit and nut trees, herbs, insects, animals, birds--all of nature--are encouraged to flourish in the BFI garden. The goal is to have a garden that can produce more and more of its own ecological needs, a sustainable edible landscape. BFI is the most methodically and persistently researched, practiced and articulated style of hand-labor gardening, with a long history of experienced practitioners.
In the Farallones Institute 1979 Annual Report, the history of the biodynamic French intensive method is described: “BFI began when Alan Chadwick initiated the garden project on the Santa Cruz campus of the University of California in 1967. He presented a synthesis of several European horticultural and cultural traditions. . . . One is the example of the French intensive system of production practiced by the market gardeners of Paris during the late 1800s. Another primary influence . . . was biodynamics, which stems from a series of talks given by Rudolf Steiner in 1924. . . . At these lectures, the farmers were asked to investigate deeper influences, such as the character of the minerals in the soil and the influences of the cosmos, to gain a more holistic sense of their agricultural practices. The approach identified a reverence for some of the aspects of peasant life and wisdom . . . asked that we acknowledge the vital or life force as something ultimate and self-sustaining . . . (and view) humans as an instrument between heaven and earth, working to enhance and quicken biological dynamics. Chadwick himself created a special atmosphere within his gardens, an unmistakable vibrancy and brilliance.”
Although double-digging the soil is the most familiar aspect of BFI, there are other equally important cultural guidelines. Close plantings are favored because of the beneficial microclimate that is produced beneath the continuous cover of foliage. When all the leaves are touching, the soil is cooler and healthier. Each plant grows more regular and robust. Once the soil is shaded by the canopy of the foliage, fewer weeds can germinate. Much less water is required with BFI than with conventional gardening because of the combined effects of the deeply cultivated soil, the addition of compost, the “living mulch” of the crops’ foliage and the interplanting of deep- and shallow-rooted vegetables.
There are natural models for the BFI method; double-digging is meant to duplicate the conditions present in landslides and sand bars. Chadwick often mentioned the observation by the Greeks that plants proliferate on a landslide because of the loosened soil. The incorporation of air into the soil during a landslide allows for easier penetration by roots and a greater availability of moisture and nutrients. The rounded shape and the fractured soil of a landslide increases its surface area and is thought to allow for a healthier exchange of gases between the earth and atmosphere--the waste gases of soil life (carbon dioxide, sulfur dioxide and others) being replaced by the growth-stimulating gases oxygen and nitrogen, among others.
Another example of naturally loose, fertile soils can be found in the gravel, silt and sand deposited each season in river beds. In both situations, the soil has been deposited with larger pieces at the bottom and finer particles closer to the surface. This stratification of particles encourages the upward capillary action of moisture from deeper supplies.
The dense spacing of plants is a distinctive characteristic of the biodynamic French intensive method. With more roots growing downward rather than sideways in pursuit of nutrients, vegetables can be planted closer together.
BFI gardeners make beds 2 1/2 to 5 feet wide at whatever length is desired. Permanent paths separate the beds; cultivated soil is never walked on. The soil in the beds remains loose and friable, and its surface is noticeably raised, due to the distinctive BFI type of cultivation. The BFI gardener loosens the soil as deeply as 24 inches without turning or churning it. With a spading shovel, the gardener removes the top 10 to 12 inches of soil, making an open trench across the width of the bed. Each spadeful of soil is heaved forward--as it hits the ground, it is aerated and “texturized,” though the natural layers are preserved. A spading fork is used to fracture the subsoil 10 to 12 inches deep in the trench. The gardener moves backward and creates a second trench across the bed, heaving forward the spadefuls of soil to fill the first trench. These steps are repeated the length of the bed. The critical detail is the avoidance of inverting the soil. “How to Grow More Vegetables Than You Ever Thought Possible on Less Land Than You Can Imagine,” by John Jeavons, is required reading if you are serious about double-digging and the BFI method.
The dense, close spacing of plants is another distinctive characteristic of BFI gardening. Roots penetrate deep in the beds, not having to spread to the sides to find nutrients. With more roots growing downward rather than sideways in pursuit of nutrients, vegetables can be planted closer together. The spacing recommendations are much closer than most gardeners are used to, and so demand deep cultivation. Broccoli, for instance, is usually planted 18 inches apart in the row with 30 inches between rows. Using BFI, it can be planted with only 15-inch spacing between plants and rows.
BFI gardeners can plant a quick- growing vegetable such as lettuce with slower-maturing vegetables such as broccoli. The lettuce aids the broccoli by rapidly covering the soil with a protective canopy. By the time the lettuce is ready to harvest, the broccoli has grown large enough to provide its own living mulch.
JEAVONS DEPICTS THEm any benefits of BFI statistically in an often-quoted passage: “Our initial research seems to indicate that the method can produce an average of four times more vegetables per acre than . . . mechanized and chemical agricultural techniques. The method also appears to use 1/8 the water and 1/2 to zero the purchased nitrogen fertilizer and 1/100 the energy consumed by commercial agriculture, per pound of vegetable grown.”
A closer look at the origin of these figures will temper the claims. A footnote indicates that the energy figure is for the assumed condition of soil after five years of improvement, even though only three years of actual testing were done, and states that the figure does not include unproductive plots, which covered 10% of the area. So the full savings are not to be realized immediately but only after a lot of hard work--unless you begin with a good soil. Virtually any method of hand-labor gardening uses far less energy (measured
in calories expended) than machinery. People are more efficient at expending calories than machines (although not as speedy nor as persistent). Jeavons estimates that the energy inputs per unit of area in most hand-gardening systems are similar, but the BFI yields are much higher per unit of labor. All things considered, the BFI method certainly uses considerably less energy than typical agriculture.
FERTILITY IS ENHANCED by the exchange of gases between the soil and the atmosphere. The channels for the movement of gases are called the soil’s pore space. These form an extensive labyrinth of minute conduits. The “heavier” the soil, the less extensive are the passageways. Undisturbed soils slowly evolve a friable soil that is up to 50% pore space, through the action of worms, bacteria, fungi and roots--processes that take decades. If you are beginning with a poor soil, start out with wider spacings between plants. Your soil’s fertility and structure will improve over time.
Pore space is very different from air pockets. Much of the tilth (crumbly structure) of a recently cultivated soil is from relatively large air spaces. These do not provide the same benevolent influences as a soil with good pore space. Although water can just as easily drain downward, upward capillary action is impeded, root hairs are killed by the excessive air, and organic matter can be more easily oxidized.
When the soil is just moist enough for proper cultivation, it is also the easiest to work. Conversely, if you feel as though you are working against the soil--it is sticking to your shovel and the clods aren’t breaking easily--the soil is too wet. Take a break until the soil is drier and easier to work.
Working the soil is the most strenuous part of the BFI method. Jeavons estimates that the initial preparation of a 100-square-foot bed will take 6 to 14 hours. Two to four of these hours are spent double-digging. The remaining hours involve activities that would be done with just about any type of gardening-- weeding, watering, shaping the beds, fertilizing and planting. (Subsequent preparation is reduced to no more than three hours of double-digging and less than four hours of other activities.)
The hotter the climate, the more you should consider whether or not raised beds are truly beneficial, especially with sandy soils. Sandy soils are likely to be low in nitrogen and organic matter; too much intensive digging may only exaggerate these problems. The hotter the summer climate, the faster organic matter is consumed. The more frequently you dig soils in hot summer weather, the more material you will need to add to compensate for oxidation. However, once the living mulch covers the bed, it will help to moderate high soil temperatures. In a hot, dry summer climate, the soil in a raised bed may not only heat up too much but also be vulnerable to drying out--thus negating one of the benefits of BFI.
A preoccupation with maximum yields per square foot is necessary only for ambitious gardeners with the smallest of yards. There is less reason to use BFI beds or interplanting if you have a large backyard. The lower yields produced by other methods of cultivation can easily be compensated for by simply planting an area that is two to four times larger, although more water and fertilizers will be needed. In many backyards, this will require only a small portion of the yard. Fast-growing, high-value salad greens such as Bibb lettuce, escarole and endive are an excellent choice for a small BFI bed nearest the kitchen door, though even lettuce may not need deep cultivation if the soil is good.
Dense plantings may encourage specific diseases in certain climates. For example, in humid, rainy summer areas, tomatoes need all the air circulation they can get to avoid mildew and leaf blights. Rather than the dense plantings recommended by Jeavons, a better strategy would be to allow plenty of space between the foliage (reducing or eliminating the living mulch effect) by double-digging individual planting holes much farther apart than 18 inches. In some climates, you may want to leave several feet or more between the leaves of mature tomato plants; that may mean that the seedlings are placed as far apart as four feet. Also, make sure to prune off much of the lower foliage as soon as the plants begin to set fruit. That will help encourage air circulation beneath and around the plants. A straw mulch, instead of the foliage of the tomato plants, could easily protect the soil between plants from sun and erosion problems. Keep the mulch away from the base of each tomato plant to avoid stem rot. In hot, humid climates the mulch may encourage the spread of root rots in the soil, in which case more bare soil may be preferable.
Once the soil is of good tilth, deep digging is not required every year. After a period of soil improvement, the bed can be maintained with a simple surface preparation and a seasonal application of compost. The Irish have even called established raised beds “lazy beds.”
From “Designing and Maintaining Your Edible Landscape--Naturally,” by Robert Kourik, distributed by Rodale Press. Copyright 1986 by Robert Kourik, Metamorphic Press , Santa Rosa. Reprinted with permission.