Sulfur Fertilization of Bahiagrass with Varying Levels of Nitrogen Fertilization on a Florida Spodosol

Low levels of available S in soils may limit bahiagrass ( Paspalum notatum Flugge) growth in Florida. To characterize the response of bahiagrass to S fertilizer, we annually applied a factorial combination of four N (N 0 –N 255 = 0, 85, 170, and 255 kg ha −1 , respectively) and S (S 0 –S 285 = 0, 95, 190, and 285 kg ha −1 , respectively) levels to a >40‐yr‐old pasture and measured forage yield, N and S concentrations, and N and S uptake at 35, 70, and 105 d after fertilization (DAF) over 3 yr. There were highly significant N × S fertilizer interactions for yield, concentration of N, and N uptake. In the absence of N, each of these responses increased with increasing rates of S, but as level of N increased, these three responses to S diminished. For example, with N 0 , yield ranged from 1140 to 2640 kg dry matter (DM) ha −1 over S 0 to S 285 , but with N 255 , yield did not vary (mean 3210 kg DM ha −1 ). Up to 80 kg N ha −1 yr −1 came from apparent mineralization of soil organic matter (OM) as a result of addition of S to plots that received no N. At 35 DAF, concentrations of S in forage ranged from 2.6 to 3.8 g kg −1 with S 0 to S 285 . Maximum annual uptake was 28 kg S ha −1 with recovery at 136 g S kg −1 of applied S. With 56 to 67 kg N ha −1 yr −1 , as is common on Florida ranches, fertilization with S may not be necessary on older pasture.