The great zucchini glut -- and complacency about world soil

THE annual race between man and the tomato hornworm has crossed the finish line once more. As always, each contender has grabbed some of the prizes. Gluts of zucchini, tomatoes, and squash threaten to dwarf Europe's butter mountain. Surplus from backyard gardens is shunted from household to household, as proud amateur hoe-hoe-hoers unload their zucchini on office associates and neighbors -- who are themselves turning their oversupply into frozen zucchini bread.

In midsummer, nearly everyone in this urban, cybernetic, 512K RAM world becomes a minifarmer -- at least to the extent of trying to cage and tame a hydraheaded tomato or two.

Given this annual rite of returning to our roots (literally roots), it's amazing how little attention we collectively pay to the soil.

``Are you kidding?'' you say. ``Have you seen the stains on my knees lately?''

That's not what's at issue. We may be knee deep in our backyard patch. But as a society we are much more concerned about what is happening to air and water than what is happening to the world's soil.

True, we have long paid attention to pesticide buildup and runoff on farmland. And we are momentarily cautious if a product of the soil is wrongly sprayed, as broccoli and watermelons recently were in California.

But the soil itself (that thin skin that shares our planet's name and, along with air, water, and sun radiation, makes Earth habitable) does not get the kind of attention it should from our civilization.

We have begun to pay heed. For decades we have talked about fending off urban sprawl as it threatens rich truck-farm land. Or diverting highways as they pave over alluvial bottomlands. Lawmakers in much of the industrialized world have passed farm easement legislation that defers a portion of taxes on farmland in danger of being swallowed, unless or until it is developed. And the industrialized world is beginning to watch with concern the erosion and leaching occurring over large stretches

of what was once tropical rain forest.

In many countries, however, more attention should be paid to the dangers of farming marginal land. Erosion by rain and wind is an obvious problem. Stretching irrigation systems beyond their capacity to deliver in the dry end of the climate cycle is another long-term risk.

The greatest long-range risk of all, though, is one least noticed by the average citizen or lawmaker. That is the gradually changed composition of soils themselves.

There are several ingredients of this change. One is gradual loss of nutrients and trace chemical compounds. A second is the opposite: buildup of undesirable chemical compounds -- especially in the subsoil. A third is gradual loss of tilth. More on that in a moment.

First, look down on the globe and try to imagine a time-lapse film of human history since tribes first settled down to cultivation (in both senses of the word). You would see, in such an astronaut's-eye film, a very gradual increase -- then a geometric increase -- in the flow of harvests from countryside to city. Food, fiber, timber, and packaging materials would trickle, then gush, into cities as urban areas, transportation networks, and factory farming expanded. At the same time the pace of steam shov els digging into guano deposits and phosphate banks would quicken as fertilizer plants supplemented and then outstripped traditional manure and green-manure methods of soil enrichment.

To some extent organic farmers have been wrong about the upsurge of chemical fertilizers. An atom of nitrogen is an atom of nitrogen no matter whether it is delivered by a nitrogen-fixing nodule on a pea root or by a synthetic ammonia compound. But in one enormously important aspect the organic farmers have been right. Chemical fertilizers that are not completely used by plants can leave residues in the soil and subsoil if not adequately flushed out. Some of these residues are believed to cause diminish ing yields in certain plants. At the same time, certain chemical elements of a good soil may be leached out, or sent to market and never returned.

Loss of tilth is more subtle. Tilth rates exactly 10 unenlightening words in my desk dictionary. It is a term that defines not only the workability of soil, but its permeabililty to root growth, water, and air; its ability to retain water; its ability to retain and gradually feed out nutrients; its ability to buffer oversupplies of certain elements. To recycle tilth, farmers have for millenniums plowed back into the soil stubble, manure, cover crops, and compost.

As erosion, leaching, residue buildup, and the shipping of unreplaced elements to market continue, the industrial world will need to do more about solving these problems. We need more research on soil damage and what to do about it. That means, for example, speeding the genetic designing plants that affix their own fertilizer. It means developing new farming methods.

Looked at in astronaut perspective, we probably need most of all to find ways to send some of our urban waste products back to the land from which they were harvested. Any backyard tomato-grower who uses both commercial fertilizer and compost knows that.

Earl W. Foell is editor in chief of The Christian Science Monitor.

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