Sugarcane Yield Response to Nitrogen On Mineral Soils in Florida.

Sugarcane (Saccharum  spp.) is grown on about 33,000 ha of mineral soils in Florida. Any major expansion of sugarcane or energy cane will be on these mineral soils because all available Histosols in the Everglades Agricultural Area are already in crop production. The current UF/IFAS recommendation for sugarcane on these soils is 202 kg N/ha/yr. Growers have voiced concerns in recent years that this level of N is not sufficient for economic production on these soils. The objective of this study is to determine economically and environmentally viable N recommendations for sugarcane grown on sandy soils in Florida. Nitrogen rate experiments were established at four locations using soluble N applications (ammonium nitrate and diammonium phosphate). There were three locations with 157, 202, 246, 291, and 336 kg N/ha/yr applied as 4 vs 5 (plant) or 3 vs 4 (ratoon) split applications in randomized complete block designs. A fourth experiment was set up as a Latin square design with 0, 67, 134, 202, and 269 kg N/ha/yr applied in 3 split applications. There were 4 plant cane crops and 5 ratoon crops considered in the analysis. Strong responses of t sugar/ha to N application were determined, with the degree of response depending on crop year and location. Exponential models indicated that 95% of sucrose yield relative to that predicted for the 336 kg N/ha rate was achieved at 240 and 220 kg N/ha/yr for plant and ratoon cane, respectively. These results can be used to develop appropriate N recommendations for plant and ratoon sugarcane crops.