Science: Sense About Soil

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Never before has farming been so full of faddists making loud claims and crying simple cures. In the latest issue of the authoritative Scientific Monthly, Dr. Charles E. Kellogg, head of the Division of Soil Survey, U.S. Department of Agriculture, assesses them all with a skeptical eye. Some of the popular theories, he believes, have good things in them, but none of them tell the whole story.

The oldest of the fashionable farming theories, says Dr. Kellogg, teaches that "the soil is like a bank"; the farmer must deposit (in fertilizer) as much as he takes out (in crops), or eventually overdraw his account. This is true only in certain cases, says Dr. Kellogg. Many soils can be cropped indefinitely without loss of fertility. The chemical elements taken away by crops are restored by silt, dust and volcanic ash. Other chemicals work their way up from below. Dr. Kellogg does not believe that fertilizers are unnecessary, but he thinks that farmers who follow the "bank" theory often waste money by applying "complete" fertilizers that their soils do not need.

Friendly Erosion. Erosion is another menace that Dr. Kellogg thinks has been oversold. Some soils erode badly, he says, but others do not, even on steep, long-cultivated slopes. Great gullies cutting through a field destroy its value, but gradual erosion does little harm and may even be beneficial. When the topsoil washes gradually away, the subsoil may turn into topsoil with renewed fertility. "Much [erosion]," says Dr. Kellogg, "is a perfectly normal concomitant of mountain building and wearing down ... An important part is essential to the formation of productive soils. One cannot, or should not, try to stop erosion, but rather to control it."

To others, "nature's rich, black topsoil" has almost mystical value; once lost, it can never be restored. The fact is, explains Dr. Kellogg, that many virgin soils, especially in the forested eastern U.S., were not productive originally; they had to be nursed to fertility. Some highly productive soils never had a dark upper layer.

Plowless Folly. Nor does Dr. Kellogg think much of "plowless farming," a fad promoted by Edward Faulkner's Plowman's Folly. Sometimes, Kellogg says, it is a good idea to avoid plowing, so as to leave a layer of litter on the surface, but the plowless method works only in special cases. "Some farmers and gardeners," says he, "in the eastern part of the U.S.—especially city gardeners—took the doctrine literally and planted corn in fields of Bermuda grass—corn that got a few inches high, turned yellow, and finally perished."

Another agricultural cult popular with city gardeners is "organic farming." Organic matter is an important component of soils, says Dr. Kellogg, "but the advocates of the organic matter doctrine go very far. They insist that ... the usual chemical fertilizers are downright poisonous to soils; that the liberal use of compost gives special qualities to plants—they will be free of insects and diseases; and that animals, or even people, will be ever so much more healthy by eating plants grown 'the organic way.' " Most of this is silly, says Dr. Kellogg politely. Organic compost is no cureall, and chemical fertilizers no "poison."