Soil solarization is regarded as an environmentally friendly alternative to pesticides for controlling nematodes, weeds and disease. Sheets of plastic (generally clear) are spread over the ground and solar energy heats the soil underneath to temperatures as high as 55C (or 131F). Since the soil environment is usually insulated from temperature extremes, the organisms that live there are unlikely to be resistant to heat stress.
This is a practice best suited to agricultural production, where monocultures of plants have attracted their specific diseases and pests. Decades of research have shown success in controlling pests in greenhouses, nurseries, and fields. But there’s a down side to this chemical-free means of pest control.
It shouldn’t be surprising that beneficial soil organisms, in addition to pests and pathogens, are killed by solarization. Studies have found that soil solarization wipes out native mycorrhizal fungi and nitrogen-fixing bacteria. One expects that other beneficial microbes, predacious insects, and parasitoids living in the soil (but so far unstudied) would be eliminated as well.
This may be an acceptable loss to those who are producing crops; soil can be reinoculated with mycorrhizal fungi, for example. But for those of us caring for our own gardens and landscapes, this is literally overkill. (And consider that most of us probably have trees and shrubs whose fine roots extend over our entire property.)
So this spring, instead of solarizing your soil, consider some less drastic measures of pest and disease control. Minimize soil disruption to preserve populations of desirable microbes. Plant polycultures (more than one species) in your vegetable garden, or at least practice crop rotation. Protect and nourish vegetable gardens with compost. Use coarse organic mulches, which provide habitat for beneficial insects and spiders, in landscaped areas. Above all, try to treat your soil as the living ecosystem it is, rather than a war zone.
