Simulation of N2O Emissions From Two Cool Season Turfgrass Lawns Using the Daycent Model.

Nitrous oxide (N₂O) emissions are an important component of the greenhouse budget for turfgrasses.  To estimate N₂O emissions from home lawns, the DAYCENT ecosystem model was parameterized and applied to turf ecosystems.  The annual cumulative N₂O emissions predicted by the DAYCENT model were close to the measured emission rates of Kentucky bluegrass lawns in Colorado (within 16% of the observed values).  For the perennial ryegrass site in Kansas, the DAYCENT model overestimated the N₂O emissions for all treatments by about 200% (urea and ammonium sulfate at high rate and urea at low rate).  After including the effect of biological nitrification inhibition in the root exudate of perennial ryegrass, the DAYCENT model simulated the N₂O emissions for all treatments within 8% of the observed values.  After calibration and validation, the DAYCENT model was further used to simulate carbon sequestration and N₂O emissions 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 years  would  significantly reduce long-term N₂O emissions by approximately 40% when compared to applying N at a constant rate (at 150 kg N ha^-1 yr^-1).