When it comes to soil and genetic engineering, proceed with caution

THERE'S a new note of caution for applying the wonders of genetic engineering down on the farm. Unexpected effects may show up where farmers least expect them - in their soils.

Plants and microbes genetically altered to be pest resistant, more nutritious, more productive, or otherwise improved are carefully evaluated to make sure they do not harm the environment. But the environment considered has not included the soil.

That would have been a serious mistake with a genetically engineered bacterium that can help break down farm wastes to make ethanol. It had passed the usual scrutiny. A more sophisticated evaluation at Oregon State University at Corvallis has shown the bacterium could harm a farmer's soil.

Reporting this earlier this month at the Biological Society of America's annual meeting in Knoxville, Tenn., Oregon State botanist Elaine Ingham explained: ``Biotechnology is not a problem in itself. But we may have to be more careful about the way it's applied. Some existing tests have not given us all the information we need to evaluate the impact of some biotech products in complex, real-world systems such as soils.''

Soil is more than ``dirt.'' It's a complex living web in which a variety of organisms interact to process organic matter, recycle nutrients, and nurture one another. While this includes larger organisms such as earthworms, it's the microscopic community that underlies the system. There are tens of millions of bacteria and tens of thousands of protozoa and other tiny animals in a gram of good top soil. Some of the most important community members are fungi. Beneficial soil fungi are essential to the health of plants whether they grow in a forest or a wheat field.

Using a new soil research system at Oregon State, Dr. Ingham and Michael Holmes tested the new genetically engineered bacterium - Klebsiella planticola. Its ability to speed the fermentation of farm wastes to make ethanol could aid industrial production of this fuel additive. However, the bacterium could also be used directly in the field to break down residual stubble, or leftover waste from ethanol production might be used as fertilizer. It turns out that the bacterium would persist in soil. The ethanol it produced hurt the fungi. That, in turn, hurt plant growth and cut seedling survival. The bacterium might still be safely used in an ethanol factory. But it has to be kept out of the soil.

The need for soil-safety evaluation of genetically engineered organisms is growing swiftly. More than developing useful bacteria or improving food production is involved.

For example, David Russell, director of plant molecular biology at Agracetus in Middleton, Wis., says that plants may be engineered to ``grow'' industrial and pharmaceutical chemicals. He explained at the American Chemical Society annual meeting in Washington that some useful chemicals ``are just too expensive to produce'' using normal industrial methods. But, with genetic engineering, a cornfield could become a chemical factory.

Meanwhile, the United States has relaxed its rule on release of organisms genetically engineered to kill crop pests. For field tests on small plots and only for genetic changes similar to those believed to occur naturally, researchers no longer need Environmental Protection Agency approval. This speeds such research. But it also relaxes a level of caution.

Clearly, the potential economic payoff of agricultural genetic engineering has reached a point where it will drive rapid development. Oregon State has done more than flag an unwise use of a nifty biotech product. It raises a general warning not to rush new plants and microbes onto the farm without knowing what they might do to a farmer's most precious resource - the soil.