Microbial and soil properties in bentgrass putting greens: Impacts of nitrogen fertilization rates

Nitrogen fertilization is important for maintaining the quality of golf course putting greens, but causes environmental concerns and affects soil organic matter buildup. Belowground biology and processes are vital to address both environmental and organic buildup issues. We examined microbial and soil properties in sand-based bentgrass putting greens that had been unfertilized or fertilized at the rates of 195, 244, and 305 kg N ha−1 yr−1 for over one year after turf establishment. Nitrogen fertilization increased soil organic C by ~ 10% and slightly modified microbial community as revealed by denaturing gradient gel electrophoresis, but had no effects on microbial biomass or C and N mineralization. We observed that changes in soil pH and enzyme activities were the functions of fertilization rates. Soil pH was reduced by ~ 0.3 to 0.8 units as fertilization rates increased. The activities of soil enzymes (β-glucosidase, N-acetyl-β-glucosaminidase, chitinase, and cellulase) were enhanced by fertilization at 195 or 244 kg N ha−1 yr−1, but was equivalent to or even lower than those in the unfertilized control when fertilization rate reached 305 kg N ha−1 yr−1. Results indicated that the activity of soil enzymes could be used as an important metric to diagnose the impacts of fertilization rates on soil. Fertilization rate at approximately 200 kg N ha−1 yr−1 appeared to be appropriate for managing putting greens.

Research highlights
► Soil enzyme activities are sensitive to fertilization rates.
► A low rate of fertilization stimulates soil enzyme activity.
► A high rate of fertilization suppresses soil enzyme activity.
► Soil enzyme activities are reduced by fertilization-induced soil acidity.