Nitrogen leaching and St. Augustinegrass turf response to lawn maintenance strategies

Home lawn fertilization has been implicated as a potential source of nitrogen (N) contamination to fragile watersheds in southern Florida. A field-scale study evaluating the effect of N sources and rates, and irrigation scheduling on performance and N leaching from St. Augustinegrass lawns was conducted in South Florida. Vadose zone nitrate-N and ammonium-N concentrations were determined in percolate collected from ceramic cup samplers installed 40 cm below the soil surface. Grass clippings and root cores were collected to assess growth. Fertilization of N to recently established St. Augustinegrass at double the standard recommendation resulted in more N leaching. Conversely, reducing the recommended N rate by half did not reduce N leaching. Controlled-release N sources did not reduce N leaching, although sulfur coated urea provided better turf quality during dry season months. Frequency of irrigation was important in reducing N leaching during dry season months. Water consumption was reduced by 37% during the wet season by adjusting irrigation on a monthly basis to meet potential evapotranspiration in conjunction with using a rain shut-off sensor. Nevertheless, this irrigation scheduling was not effective in reducing N leaching. Irrigating upon visual wilt produced lower quality turfgrass that eventually required more frequent irrigation. This research also documented the influence of soil organic matter (SOM) harvested with sod on turf performance and N leaching. Nitrate-N leaching increased after sod installation, however quickly declined to pre-installation leaching losses. During dry season months, greater turf quality and growth was documented from newly established St. Augustinegrass with 100 g kg-1 SOM, however nitrate-N and total inorganic-N leaching was also greater when compared to St. Augustinegrass with 40 g kg-1 SOM. In comparison to recently established St. Augustinegrass, monitoring total inorganic-N alone was not an effective measure for determining maintenance strategies for reducing N leaching from established St. Augustinegrass. Best management practices could be optimized to provide quality St. Augustinegrass with minimizing the potential for N leaching by accounting for N contributions from SOM of harvested sod when determining N fertilization applications, seasonally adjusting irrigation schedules, and utilizing a rain shut-off sensor.