PHOSPHORUS IN DRAINAGE WATER FROM SUGARCANE IN THE EVERGLADES-AGRICULTURAL-AREA AS AFFECTED BY DRAINAGE RATE

Sugarcane (interspecific hybrids of Saccharum spp.) is grown on 78% (1 56,000 ha) of the cultivated organic soils of the Everglades Agricultu ral Area (EAA) of southern Florida. Recently, the EAA has come under s crutiny because of concerns with the impact of nutrient-rich drainage water from organic soils on the ecology of adjoining bodies of water a nd wetlands. The objectives of our research were to determine the effe cts of field drainage rate on P concentration and off-field P loads in drainage water from sugarcane grown on organic soils of the EAA and t o determine the effect of field drainage rate on sugarcane productivit y and sugar yield. The research site was on a Terra Ceia muck soil (eu ic, hyperthermic Typic Medisaprist) on a commercial sugarcane farm loc ated in the EAA. The treatments were fast and slow field drainage rate s. Nine drainage events were monitored between Nov. 1988 and Aug. 1990 . Average drainage water total P (TP) and total dissolved P (TDP) conc entrations were significantly higher for the slow drainage rate treatm ent. In order to minimize off-farm P loading, main-farm canal water sh ould be discharged off-farm while field drainage water is retained on- farm. Field drainage rate should be fast and drainage event duration s hould be as short as possible. Plant-cane crop yield and yield compone nt data were not collected. The first-ratoon crop total aerial dry wei ght and harvested sugarcane and sugar yields were not affected by drai nage rate.