The natural biocontrol ability of chitosan should not be confused with the effects of fertilizers or pesticides upon plants or the environment.

Dr. Wagner said the system could be used with lettuce and other vegetables to counteract the effects of fertilizers with high concentrations of heavy metals - municipal sludge, for example.

Intensive agriculture has become associated with decreased soil quality in India and Asia, and there has been increased concern over the effects of fertilizers and pesticides on the environment, particularly as population increases and food demand expands.

Martin Shea, Southampton's chief environmental analyst, said his town encourages the use of native plants to protect the biodiversity of the area and to lessen the adverse effects of fertilizer and pesticides to its "endless miles of wetlands."