3. Results
3.1. Soil physical and chemical properties
Soils collected from warm- and cool-season turfgrass systems did not differ in total soil C, total soil N, soil pH, or soilwater content (Table 1). Soil water content was also unaffected by sampling times (Table 2). However, soil pH varied slightly with sampling times (Table 2) and was approximately 5.6 in September 2006 and 5.9 at other times. Nitrate-N accounted for >95% of soil inorganic N in soil samples collected in September and May. While NO3- -N was the dominant form of soil inorganic N at other sampling times (i.e., December and February), NH4l - N as a fraction of soil inorganic N increased to ̴ 40% in some field plots. Nevertheless, soil inorganic N was unaffected by turfgrass types but fluctuated significantly over time (Fig. 3, Table 2). Soil inorganic N was highest in May, roughly 4-fold higher than that in February. It should be noted that May sampling took place a few days after turfgrasses were fertilized, which may be partly responsible for the high soil inorganic N content. Water extractable soil organic C and N also varied significantly with sampling times (Fig. 3, Table 2) with concentrations in May being 2e3 times greater than on other dates. However, water extractable soil organic C and N was not affected by turfgrass types (Table 2).