VEGETATIVE ALTERATION OF NITRATE FATE IN UNSATURATED ZONE

A small field site adjacent to a lake in Amana, Iowa was used to inves tigate the fate of nitrate fertilizer in the unsaturated zone. The fer tilizer was applied to a barren plot, a plot planted with corn, and a plot planted with deep-rooted poplar trees (Populus spp.) to study the characteristic behavior of a typical agricultural environment and a n ovel pollutant-interception technique in comparison to unmanaged land. Nitrate concentrations were lower in the corn and especially the popl ar plot due to plant uptake, but concentrations increased markedly in September after the plants began to shut down and nitrification occurr ed. The poplar trees were most effective in long-term nitrate reductio n; they provide perennial interception. Statistical analysis confirmed plant uptake was an important process in the fate of nitrate, and hen ce, vegetative buffer strips hold promise for protecting water supplie s.