Sugarcane Yield Response to Phosphorus Fertilizer as Related to Extractable Soil Phosphorus on Florida Mineral Soils

Relating phosphorus (P) fertilization to crop demand in sugarcane (Saccharum spp.) grown on mineral soils in southern Florida is critical for minimized environmental impact and sustained crop production. Previous P fertilizer recommendations date to 1974 and so revised recommendations are needed for sugarcane on these soils which account for 29% of the crop in Florida. Phosphorus rate studies were conducted at seven field locations (16 total site-crop years) with P rates of 0 to 73 kg P ha(-1) at Site 1 and 0 to 61 kg P ha(-1) at Sites 2-7 using small-plots (82 or 120 m(2) plots) on four soil series representing Spodosols, Entisols, and Alfisols. Soil P extractions with Mehlich 3, 0.7 M ammonium acetate, and water were evaluated in relation to relative sucrose yield and leaf P concentrations. Mehlich 3 had stronger relationships with relative yield and leaf P and a Mehlich 3 P value of 80 g m(-3) is proposed as a critical value above which no P fertilizer would be required. Without added P fertilizer, Mehlich 3-extractable P values decreased annually by an average of 20%. Results suggest maintaining 36.7 kg P ha(-1) as the maximum P fertilizer rate for sugarcane in mineral soils.