Simulation of Nitrous Oxide Emissions and Estimation of Global Warming Potential in Turfgrass Systems Using the DAYCENT Model

Nitrous oxide (N 2 O) emissions are an important component of the greenhouse gas budget for turfgrasses. To estimate N 2 O emissions and global warming potential, the DAYCENT ecosystem model was parameterized and applied to turfgrass ecosystems. The annual cumulative N 2 O emissions predicted by the DAYCENT model were close to the measured emission rates of Kentucky bluegrass ( Poa pratensis L.) sites in Colorado (within 16% of the observed values). For the perennial ryegrass ( Lolium perenne L.) site in Kansas, the DAYCENT model initially overestimated the N 2 O emissions for all treatments (urea and ammonium sulfate at 250 kg N ha −1 yr −1 and urea at 50 kg N ha −1 yr −1 ) by about 200%. After including the effect of biological nitrification inhibition in the root exudate of perennial ryegrass, the DAYCENT model correctly simulated the N 2 O emissions for all treatments (within 8% of the observed values). After calibration and validation, the DAYCENT model was used to simulate N 2 O emissions and carbon sequestration of a Kentucky bluegrass lawn under a series of management regimes. The model simulation suggested that gradually reducing fertilization as the lawn ages from 0 to 50 yr would significantly reduce long‐term N 2 O emissions by approximately 40% when compared with applying N at a constant rate of 150 kg N ha −1 yr −1 . Our simulation indicates that a Kentucky bluegrass lawn in Colorado could change from a sink to a weak source of greenhouse gas emissions 20 to 30 yr after establishment.