SUGARCANE PRODUCTION IMPACT ON NITROGEN AND PHOSPHORUS IN DRAINAGE WATER FROM AN EVERGLADES HISTOSOL

The Everglades Agricultural Area (EAA) in southern Florida is a 280 00 0-ha tract of land that has come under scrutiny by environmental, agri cultural industry, and government water management groups that are con cerned with the impact of nutrient-enriched drainage water on the ecol ogy of adjoining bodies of water and wetlands. Sugarcane (Saccharum sp .) is grown on 155 000 ha or 78% of the cultivated organic soils in th e EAA. The objectives of this study were to determine the N and P conc entrations and off-field loads in drainage water from sugarcane end fa llow fields. Sugarcane was planted in four of eight hydraulically inde pendent and similar field plots. Four plots were maintained fallow. Dr ainage water volume, and total nitrogen (TN), total dissolved phosphor us (TDP), and total phosphorus (TP) concentrations were monitored duri ng 12 drainage events during two crop seasons. For two drainage events , TN concentrations were higher in drainage water from fallow plots th at in drainage water from sugarcane plots and it was speculated that c rop uptake of mineralized soil N may have contributed to the reduction s during these events. Analysis of the mean for the 12 drainage events indicated no overall differences in TN off-field loads between sugarc ane and fallow plots. Further, no significant differences were found i n TDP or TP concentration in drainage water from sugarcane and fallow plots during any of the drainage events monitored. It was concluded th at, due to the large quantity of soil N and P mineralized and due to c rop N and P uptake, the impact of sugarcane production on drainage wat er N and P concentrations was minimal.