SOIL CHARACTERISTICS OF 2 SIMILARLY-FERTILIZED FLORIDA CITRUS GROVES WITH DIFFERENT GROUNDWATER NITRATE LEVELS

Groundwater nitrate concentrations remained sharply different at two s ites in the central part of the Florida peninsula over a two-year obse rvation period. Nitrogen (N) fertilization patterns, both quantity and application methods, and rainfall were approximately the same at both sites. The soil at the low groundwater nitrate site, at depths of 0 t o 120 cm, had a higher cation exchange capacity (CEC) and contained mo re ammonium acetate-extractable potassium (K), calcium (Ca), and magne sium (Mg). It also had a greater organic matter content, contained mor e clay in the 90 to 120-cm layer and more nitrate in the 1 to 30-cm la yer. There was a sharp difference in depth to groundwater. At Site 1 ( high nitrate levels) the water table remained steady at 4 m, while at Site 2 (low nitrate levels), it ranged from 0.9 to 1.1 m in the two we lls monitored. The aquifer at Site 1 was unconfined, but was confined at Site 2 by increasing clay contents with depth.