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

Received for publication January 8, 2004. 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 (N0–N255 = 0, 85, 170, and 255 kg ha^–1, respectively) and S (S0–S285 = 0, 95, 190, and 285 kg ha^–1, respectively) levels to a (greater than040yr-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 x 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 N0, yield ranged from 1140 to 2640 kg dry matter (DM) ha^–1 over S0 to S285, but with N255, 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 S0 to S285. 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.