SIMULATED EFFECTS OF IRRIGATION PRACTICES ON LEACHING OF CITRUS HERBICIDES IN FLATWOODS AND RIDGE-TYPE SOILS

Citrus in Florida is primarily grown on sandy soils. The potential for leaching of applied pesticides into groundwater gives rise to concern in these areas, It has been demonstrated that irrigation practices ca n exacerbate the leaching potential of agrichemicals. In this paper, t he relative movement of commonly used citrus herbicides has been simul ated for flatwoods and ridge-type soils under different irrigation sce narios. The movement of sir: citrus herbicides was simulated for on-de mand, periodic, and no irrigation. Leaching potential of the herbicide s increased in the order Norflurazon approximate to Oryzalin approxima te to Oxyflurofen < Diuron < Bromacil acid < Simazine. Calculated prob abilities of exceeding the USEPA lifetime health advisory level (HAL) were highest for periodic irrigation and lowest for the no-irrigation scenario. Further, ridge-type soils pro-oed more sensitive to pesticid e leaching than flatwoods soils, Absence of a soil subsurface horizon high in organic matter appears to be the governing factor For Myakka a nd Tavares soil series, no significant differences were observed when pesticide leaching was compared between Highlands and Manatee counties aside from the higher annual rainfall in Manatee County.