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 leach 10% of its total soil N as nitrate into ground water. This study investigated how rapidly and completely soil N can be restabilized following reseeding of killed turf. Twelve-year-old field plots, comprising four cool-season turfgrass species growing on an Enfield silt loam (coarse-silty over sandy-skeletal, mixed, active, mesic Typic Dystrudepts) at Kingston, RI, were used. In early September 1997, one-half of the plots were killed by applying glyphosate and three-fourths of the dead plots were reseeded with `Palmer III\u27 perennial ryegrass (Lolium perenne L.) in late March 1998. Soil moisture, temperature, pH, respiration, and extractable nitrate and ammonium were monitored every 6 to 8 wk. Nitrate levels in subsoil water were monitored at 2-wk intervals and nitrate leaching estimated for each percolation event. Reseeding enhanced soil respiration, within 6 wk of seeding, to levels comparable with those of soil in healthy plots. Surface soil nitrate levels in killed and reseeded plots declined within 6 wk of reseeding. Nitrate levels in soil water beneath the root zone declined in reseeded plots relative to those of healthy plots (9 mg NO3-N L-1) within 8 wk of reseeding. Nitrate leaching also declined 3 mo after seeding to rates less than half of those 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