I ONCE ASKED HANS JENNY, the dean of American soil scientists, what made a soil good. He answered with a question: “Good for what?”
Somehow, in my heart I believed he was holding out on me, concealing the recipe that would make anything grow fast and strong. I wanted to know about those proverbial soils where when you drop a seed, you have to jump back to get out of the way of the rising stalk. I did not consider that in the real world such a hot soil might easily result in wheat that grew too much stem too fast, and lodged (that is, fell right over), dropping its seed in the dust.
Neither did I think of those chunky clay soils in the upper Midwest, with a little red in their brown, that break into huge lumps when they are plowed in autumn. A corn seed falling among these chasms would doubtless be lost, I thought, as I teetered among the upturned shards in early October. I did not wait to see the mellowing action of the winter’s frosts, breaking the clods and preparing them for the spring fitting that would leave a level and fertile field.
Like every other gardener, I wanted to find the magic soil, the dirt of Eden. The eighteenth-century English agriculturalist Arthur Young called the vale in southern England between Farnham and Alton “the finest ten miles” in England. I wanted to find the finest ten acres in America.
I sent out scouts. All the friends who traveled anywhere took with them a few plastic sandwich bags. I instructed them to scrape the top half inch off any likely-looking plot of ground, get me a bagful of what was underneath, and send it. My eight-year-old son, Sam, and I would do the rest.
Soon we began to receive the sacks: red clays from the Carolinas, heavy black clods from the coastal hills of Northern California; sandy yellow soils from Florida; clay slices from a Wisconsin cornfield; alkaline soils from a Nevada basin; stony gray soils from Vermont; heavy organic bog soils from Minnesota; a whitish surface soil and its rust-colored sub-soil from a Southern pine woods; forest molds from New Jersey; red dusts from the rain shadows of the intermountain West; experimental composts made with bark and manure and fish guts.
We set them up in seedling trays, thirty-seven different samples in all, making a patchwork of the soils of America. We applied a half dozen impatiens seeds to each, watered equally, and watched.
Imagine our surprise. Nothing at all came up in the composts. Ever. The California coastal soils, from artichoke fields, gave the seeds a fast start, but the stalks keeled over. The Wisconsin field soils were not spectacular performers, but they got good average germination and produced steady growth. Seeds in a North Carolina red clay sputtered and died. A rogue soil from a Bahamas polyculture, mostly pebbles, did surprisingly well. So did the pine forest’s subsoil. But the prize soil of all was from a Wyoming basin. It had been collected by my brother while he was on a motorcycle trip in a barren stretch of country. The soil was really a red dust, so light it would rise into the air if you blew upon it, and it seemed to contain very little organic matter. Nevertheless, when we gave it steady water, we found it outperformed every other soil.
Go figure. The composts that were supposed to work magic didn’t work at all. The desert soil bloomed. What was going on here? That was when I finally began to hear what Hans Jenny had been saying, not only to me but in the tenor of his whole work. A soil was not a thing to Jenny. It was a web of relationships that stood in a certain state at a certain time. Only in Eden was a soil eternally fine. East of Eden, a soil would always start and end infertile, but in the maybe 100,000 years in between, it might go through many permutations of fertility, depending on the combinations of climate, mineral matters, organic matter, and slope.
The characteristics of a fertile soil are in the dynamics of that combination. It must not be stiff, dry, or stingy. The Romans liked to speak of the best soils as fat, sweet, and open. To them, a good soil held on tightly and let go lightly. Air, water, and nutrients were all abundant in them, yet they were not held so tightly as to clog up and cease to move. Science cannot really model such a complex dynamic. Virgil and Columella, both of whom recorded their observations of Roman rural matters, insisted that the farmer taste the soil: distill it through a wine strainer with water, and drink the liquor. The best soils had neither salinity nor bitterness, but a sweet and open taste like the smell of fertile soil when it opens in the spring.
A fertile soil transmits forces. Originally, it was the only material on the Earth that could hold water. It therefore became the theater where water, earth, and air could interact, where the earth could express itself in the endless variety of organic life.
Some scientists say that hydroponic gardening—using only water and carefully regulated nutrients—can eventually replace in-ground vegetable growing. It is more efficient and easily controllable. But there are many indications that it could not succeed in the long run. Herbert Koepf and his associates in biodynamic agriculture have experimented over a period of decades with duckweeds and other aquatics grown in strictly mineral media. Though a single generation of the plants might thrive in the mineral medium, the plants did not reproduce well. They lost their vigor and died out. Evidently, only the full soil system provides the proper dynamic.
Neither is organic matter alone a criterion for success, as our experiment abundantly demonstrated. Soils high in organic matter, like bog soils, are notoriously hostile to seeds. What seems to be best is soil that contains four or five percent organic matter and that is well watered and aerated to promote the microbial life that constantly converts the organic matter into humus.
Humus itself is a dynamic creature, comprising a fast-changing part that liberates nitrogen and micronutrients for direct absorption by plant roots, a slow-changing, stable part that holds water, and a porous material that is easy for roots to penetrate.
In the days before synthetic fertilizers, the dynamic potential of humus was so important that there existed a complex formula for calculating its value when property was sold. A person selling a farm would be paid not only for the land itself, but for the value of the prehumic “dressings” he left on the land. He would get credit for the blown-down wood in his forests and hedgerows; for the manure in his stockyards; and even for the plowings that he had done in order to stir and influence the processes in the soil.
The great connoisseurs of the soil have been those who could assess at a glance the character of a piece of land. Probably no one was ever more perceptive in this regard than William Cobbett, the nineteenth-century English author of Rural Rides. His descriptions of soil are delicious. Of the typical English soil type he writes: “The short smooth grass has about nine inches of mould under it, and then comes the chalk. . . . The grass never parches upon these downs. The chalk holds the moisture, and the grass is fed by the dews in the hot and dry weather”
This may not be Eden, but to a soil man, it is near enough. Indeed, the better part of what a husbandman knows is what lies beneath the surface of his ground.