Stabilization of soil nitrate by reseeding with perennial ryegrass following sudden turf death

Turf death can result in the mineralization of organic nitrogen (N) within the turf-soil ecosystem. if not reestablished within 12 mo, dead turf can l each 10% of its total soil N as nitrate into ground water. This study inves tigated how rapidly and completely soil N fan be restabilized following res eeding of killed turf. Twelve-year-old field plots, comprising four cool-se ason turfgrass species growing on an Enfield silt loam (coarse-silty over s andy-skeletal, mixed, active, mesic Typic Dystrudepts) at Kingston, RI, wer e used. In early September 1997, one-half of the plots were killed by apply ing glyphosate and three-fourths of the dead plots were reseeded with 'Palm er III' perennial ryegrass (Lolium perenne L.) in late March 1998. Soil moi sture, temperature, pH, respiration, and extractable nitrate and ammonium w ere monitored every 6 to 8 wk. Nitrate levels in subsoil water were monitor ed at 2-wk intervals and nitrate leaching estimated for each percolation ev ent. Reseeding enhanced soil respiration, within 6 wk of seeding, to levels comparable with those of soil in healthy plots. Surface soil nitrate level s in killed and reseeded plots declined within 6 wk of reseeding. Nitrate l evels in soil water beneath the root zone declined in reseeded plots relati ve to those of healthy plots (9 mg NO3-N L-1) within 8 wk of reseeding. Nit rate leaching also declined 3 mo after seeding to rates less than half of t hose from turf that had been killed but not reseeded. Our results indicate that the potential for increased nitrate leaching following turf death can be eliminated within 2 mo if the site is promptly reseeded.