389 ● July–September 2006 16(3) Best Management Practices for Florida Citrus Larry Parsons 1 and Brian Boman 2 ADDITIONAL INDEX WORDS. nitrate, groundwater, fertilizer, nitrogen, irrigation SUMMARY. Best management practices (BMPs) started in Florida citrus (Citrus spp.) in the 1990s and have evolved to play a major role in production practices today. One of the earliest BMPs in Florida arose from concerns over nitrate-ni- trogen concentrations in some surficial groundwater aquifers exceeding the 10 mg·L –1 drinking water standard. This occurred in an area of well-drained sandy soils known as the Central Florida Ridge that extends north and south through the central part of the Florida peninsula. State agencies could have used a strictly regulatory approach and restricted how much nitrogen growers could apply. Instead of setting arbitrary regulations, the agencies promoted a scientific-based BMP approach. A nitrogen BMP for Central Florida Ridge citrus was estab- lished, and research is now validating the earlier groundwater work on more grower field sites. The purpose of this BMP was to minimize the risk of leaching nitrates from fertilizer into the groundwater. Several important aspects of the BMP involve: 1) limiting the amount of nitrogen fertilizer applied at any one time, 2) increasing the frequency of fertilizer applications, 3) reducing fertil- izer applications during the summer rainy season, and 4) managing irrigation to reduce leaching below the root zone. Since this Central Florida Ridge nitrogen BMP was established, major BMP actions to improve water quality and reduce the quantity of runoff water have taken place in the Indian River production area of Florida’s east coast. BMPs continue to be set up in other parts of the state for a variety of plant and animal agricultural practices. In some cases, cost- share funds have been provided to help implement BMPs. With voluntary BMPs, growers have scientifically based guidelines, a waiver of liability, and an avoidance of arbitrary regulations. 1 University of Florida, IFAS, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850; to whom reprint requests should be addressed: e-mail: lrp@crec.ifas.ufl.edu 2 University of Florida, IFAS, Indian River Research and Education Center, Ft. Pierce, FL 34945. F lorida is the largest producer of citrus in the United States. Production area in the state was 748,555 acres in 2004. Even after damage from several recent hurricanes, Florida produced 7,588,000 tons of citrus in 2004–05. Most citrus is grown in central, southeastern, and south- western Florida. Well-drained sandy soils extend north and south through the central part of the Florida penin- sula. The primary area from Clermont to Lake Placid is commonly called the Central Florida Ridge (Jackson, 1991), and much of the state’s citrus was grown there in the past. Soils in this area are classified as Entisols which are deep well-drained, highly permeable soils which have >95% sand, <3% clay, and <2% organic matter. They have good aeration, but are inherently low in fertility, organic matter, and cation exchange capacity. Drainage often can be excessive in these soils. They are un- able to hold much water or much of the mineral elements applied by fertilizers. Citrus is also grown on lowland soils with a sandy surface, which are classi- fied as Alfisols or Spodosols. These are usually poorly drained soils near the coast and are referred to as flatwoods soils (Jackson et al., 1995). They com- monly have drainage-impeding layers at less than 1 m. Spodosols have an acidic hardpan of aluminum or iron and organic matter while Alfisols have a subsurface clay layer. The water table is commonly close to the surface, and these soils must be bedded and drained for successful citrus production. Annual rainfall on the Florida peninsula is more than 1200 mm, and because the Entisols of the Central Florida Ridge are very well drained, Units To convert To convert U.S. to SI, SI to U.S., multiply by U.S. unit SI unit multiply by 0.4047 acre(s) ha 2.4711 1 cbar kPa 1 0.3048 ft m 3.2808 0.4536 lb kg 2.2046 1.1209 lb/acre kg·ha –1 0.8922 1 ppm mg·L –1 1 0.9072 ton(s) Mg 1.1023