Annual Nitrogen Requirement of Bahiagrass Lawns Maintained in Sub-Tropical Climates

Current best management practices (BMPs) regarding the application of nitrogen (N) to bahiagrass (Paspalum notatum Flügge) in southern Florida are 98 to 196 kg ha⁻¹ yr⁻¹. This range has not been tested to determine if the range adequately produces quality bahiagrass without adversely contributing to nonpoint source additions of N to ground water. The objectives of this research were to determine the N necessary to support acceptable bahiagrass quality by measuring associated color, growth, and nitrate-N (NO₃–N) leaching. Research was conducted from October 2006 to October 2008 in Fort Lauderdale, FL. Nitrogen was applied in 60-d cycles at rates of 49, 98, 196, or 294 kg ha⁻¹ yr⁻¹ under two irrigation regimes (2.5 mm d⁻¹ and 13 mm three times weekly). Bahiagrass quality and color was acceptable under each N rate during each cycle and regression indicated application of N to bahiagrass was not necessary to produce acceptable turfgrass. Nitrate-N leaching was unaffected by N rates during each cycle except during Cycle 3 of 2008 when the 196 and 294 kg ha⁻¹ yr⁻¹ led to 93 and 94% greater leaching, respectively, than the 49 kg ha⁻¹ yr⁻¹. The high-irrigation regime increased NO₃–N leaching by as much as eightfold but was not consistent among cycles. If current N recommendations were revised downward (~49 kg ha⁻¹ yr⁻¹), bahiagrass quality would remain acceptable and the risk of NO₃–N leaching would be reduced.