Zc. Jiang et al., Mobility of soil nitrogen and microbial responses following the sudden death of established turf, J ENVIR Q, 29(5), 2000, pp. 1625-1631
The stability of nitrogen within a turf-soil ecosystem is important both fo
r efficient turf management and preventing the contamination of ground wate
r 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, act
ive, mesic Typic Dystrudept) at Kingston, RI. Half of the plots were killed
with glyphosate in early September and any regrowth was removed mechanical
ly. 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 amm
onium. Nitrate levels were higher in both the root zone and at 60 cm follow
ing turf death and this difference persisted for the sampling year. Carbon
mineralization and microbial biomass C were not different between soils fro
m healthy and killed plots. Killed plots leached three times more nitrate t
han healthy plots but this amounted to less than 10% of total soil N presen
t. Retention of nitrate in a turf-soil system depends on absorption by livi
ng grass roots, although reasonable N stability is also provided by N cycli
ng within the soil microbiota. Protecting ground water from nitrate contami
nation is optimized by maintaining a vigorous turfgrass cover.