The stability of nitrogen within a turf‐soil ecosystem is important both for efficient turf management and preventing the contamination of ground water by nitrate. The objective of this study was to quantify responses of the microbial community and the mobility of soil nitrogen following the sudden death of established turf. Twelve‐year‐old turf plots comprising four cool‐season turfgrass species fertilized with five N sources were maintained on an Enfield silt loam (coarse‐silty over sandy or sandy‐skeletal, mixed, active, mesic Typic Dystrudept) at Kingston, RI. Half of the plots were killed with glyphosate in early September and any regrowth was removed mechanically. Measurements of soil physical, chemical, and microbiological properties and nitrate leaching in killed and healthy plots were compared for 12 mo. Turf death did not alter soil moisture, temperature, pH, or extractable ammonium. Nitrate levels were higher in both the root zone and at 60 cm following turf death and this difference persisted for the sampling year. Carbon mineralization and microbial biomass C were not different between soils from healthy and killed plots. Killed plots leached three times more nitrate than healthy plots but this amounted to less than 10% of total soil N present. Retention of nitrate in a turf‐soil system depends on absorption by living grass roots, although reasonable N stability is also provided by N cycling within the soil microbiota. Protecting ground water from nitrate contamination is optimized by maintaining a vigorous turfgrass cover.

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’ 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.