Sugarcane Yield Response to Nitrogen on Sand Soils

Maintenance of sufficient crop N for optimum sugarcane (Saccharum spp.) production on Florida mineral soils is critical but difficult because of high rainfall and the leachable nature of the sand soils. This study was conducted to determine sugarcane yield response to N on mineral soils in southern Florida and to revise current N recommendations. Four test sites were established on mineral soils (one Entisol, two Spodosols, and one Alfisol) with organic matter content of 7.2 to 16.9 g kg(-1). Annual soluble N rates of 157, 202, 246, 291, and 336 kg N ha(-1) were applied at Sites 1 to 3 and 0, 67, 134, 202, and 269 kg N ha(-1) were applied at Site 4. Comparisons of four vs. five split N applications were made in some cases and three vs. four in other cases. Exponential models for plant and ratoon crops predicted 95% of maximum relative sucrose yield at 240 and 220 kg N ha(-1), respectively, demonstrating yield response to rates higher than the current recommendation of 202 kg N ha(-1). There were no yield differences between four and five split N applications for plant or ratoon crops, but one of two ratoon crops had increased sugarcane yield with four applications compared to three. Proposed N recommendations for plant and ratoon crops are 202 to 252 kg N ha(-1) in four to five split applications and 172 to 222 kg N ha(-1) in three to four split applications, respectively.