Environmental Engineering Reference
In-Depth Information
healthy soil environment. A plant environment such as a forest can
maintain itself for thousands or, in the case of tropical rain forests,
millions of years without decline. Several rules are clear:
Multicropping is the rule. Nature never attempts monoculture, which
depletes the soil of selected nutrients.
Nature mixes plants and animals. Crops are always raised in conjunc-
tion with livestock.
The balance between growth and decay is strictly maintained. What
grows dies, and in dying is returned to the soil.
Soil Pollution
Given that the soil nourishes the plants that grow in it, and given that
a great variety of living organisms in the soil contribute to a plant's
health, it is little short of astonishing that farmers in the United States
are so willing to spray poisons on their crops and into the soil. The
United States consumes 35 percent of the world's pesticides.
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Cereal
crops are sprayed an average of fi ve or six times a season; potatoes thir-
teen times; apple trees eighteen times; and peaches are sprayed with
forty-nine assorted pesticides and fungicides on a weekly basis from
March until harvesting in July or August. Apples and peaches are the
most contaminated produce in the supermarket.
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And these artifi cial poisonous chemicals are not the only harmful
concoctions routinely added to the soil. Even the “pure” NPK (nitrogen,
phosphorous, potassium) fertilizers that nearly every commercial farmer
and gardener uses contain poisons. An analysis of twenty-nine com-
mercial fertilizers by the U.S. Public Interest Research Group revealed
that each of them contained twenty-two toxic heavy metals. In twenty
of the products, levels exceeded the limits set for waste sent to public
landfi lls.
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Most pesticides destroy a broad range of living organisms, many of
them either harmless or benefi cial—like ladybugs, praying mantises, and
earthworms—along with the undesirable pests. The appalling devasta-
tion of soil organisms caused by agricultural pesticides was well described
by a farmer who switched from conventional to organic farming. He
examined his alfalfa fi eld after applying a potent insecticide and found
“there was nothing but dead bugs, dead birds, dead worms—and little
alfalfa shoots. Hardly any of the dead things were crop pests. We stood
in amazement. It was shocking. It was the last time I ever did anything
like that.”
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