Nitrogen fertilization and return of turfgrass clippings are likely to alter soil microbial ecology. We examined soil organic matter decomposition and soil enzyme activities in two contrasting turfgrass chronosequences with soil pH values of ~6 versus ~8. Soil microbial biomass, basal respiration and N mineralization increased significantly with turfgrass age. The effects of mineral N addition on soil N mineralization and nitrification varied with soil pH, with increased mineralization and nitrification in alkaline soils but not in acidic soils. Similarly, basal respiration and microbial quotient were much higher in alkaline compared to acidic soils, suggesting that soil pH is a critical factor determining organic matter decomposition. While addition of mineral N significantly reduced the activity of soil chitinase, the addition of grass clippings enhanced the activities of chitinase, cellulase, glucosidase and glucosaminidase and these increases were more pronounced in the young compared to older turfgrass systems. By contrast, phenol oxidase activity did not change in response to addition of mineral N or grass clippings.