Any natural, uncultivated field or forest soil without insects living in it would probably be poor. However, a carefully tended Gardener's Loam without insects and other harmful pests (or at least a minimum population of them) is not only possible but desirable.
Discovery of chlorinated hydrocarbons of high potency (beginning with D.D.T. during World War II) gave us weapons of amazing efficiency to use against harmful soil-inhabiting pests. Properly used (they can be abused) these are not only safe to handle but endure for years in soil. No gardener can really appreciate their value until he has seen a lawn completely freed of grubs for four or five years with a single application of a chemical such as chlordane.
Such potency against insects naturally raises fears of the effects of these chemicals on human beings and animals. Oddly enough, most insecticide materials of this type are actually less dangerous to higher animals than are older chemicals they replaced. A case in point is chlordane which took the place of lead arsenate as a turf treatment against grubs. Chlordane is so safe that it is approved for use (with only normal caution) as a household insecticide, for spraying living quarters, basements, kitchens and other areas where the old lead arsenate would be highly dangerous. Arsenate of lead has been responsible for many deaths: I have yet to hear of a single person being killed by chlordane.
Other equally effective chemicals are available for use on insect species not too easily killed with chlordane. Most of these materials are rather specific in their action and not as useful as chlordane for a general insect-proofing treatment.
Buildup of harmful insecticide residues in soil is possible, even though the material used is quite safe to apply. Such accumulations are almost always the result of misuse and failure to follow directions.
Insecticide residues harmful to plants are not new; injurious effects of copper following regular use of Bordeaux mixture on grapevines in France were reported in the nineteenth century. One of the earliest such reports in America goes back to 1908-it dealt with arsenate of lead accumulation in an apple orchard.
Soil type has a great deal to do with harmful effects of such residues. For example, the home owner who has established a lawn after years of work on a sandy loam, only to find it infested with grubs, would do well to think twice before using arsenate of lead or calcium arsenate as a grub control.