In popular perception, the ultimate erosion site is one in which all the soil is stripped away and only bedrock is left. In reality, however, some form of "subsoil" normally remains (as in this case in Indonesia). The site may have lost all of what scientists call "weathered soil"—the upper part that had been exposed to air, rain, heat, cold, plant life, microbes, and the other natural forces that create a friable foundation for vegetation to grow in. But in most cases, something approximating soil remains.

This so-called subsoil is uninfluenced by biological activity, and few plants can grow in it. Vetiver is one of the few that can, at least in some cases. In fact, the grass may be the long-dreamed-of tool for getting degraded, tropical, lateritic soils (oxisols) into productive use. Even a tenuous hold on just some of these subsoils could give important benefits. Vetiver hedges backed up with other plants, especially legumes, might become a soil-recovery tool of exceptional value in these days when people fear that the world is running out of farmland. (Photo: Hugh Popenoe)

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