Potential Carbon Sequestration Under Bermudagrass Management.

Understanding the role of plant ecosystems and underlying soil as a sink or source for carbon (C) on a global scale is necessary for estimating changes in atmospheric CO₂ concentration.  Despite its large-scale presence in the urban ecosystem, the role of turfgrass in C cycling has received only limited study, and evaluations in warm-season turfgrasses is lacking.  The objective of this study was to estimate C sequestration in soil as affected by sampling depth and bermudagrass (Cynodon dactylon x C. transvaalensis) nitrogen (N) rate. The experiment was conducted on six-year-old ‘Tifway’ hybrid bermudagrass plots located at the Auburn University Turfgrass Research Unit. The experimental design was a randomized complete block with three replications and four N rates of 24, 49, 98, and 196 kg N ha^-1 yr^-1. Plots were sampled in summer, with the harvested bermudagrass separated into rhizomes, above ground biomass (verdure), and belowground roots.  Underlying soil samples (0-2.5, 2.5-5, 5-10, 10-20, 20-40, and 40-60 cm) were also collected. Total C and N concentrations were determined on finely ground oven-dried samples by combustion. Results showed an accumulation of organic C in the top 10 cm of the soil profile as N rate increased from 24 to 196 kg N ha^-1.