Evaluating Daycent Model Performance Estimating Soil Carbon and Nitrous Oxide Emissions in South Central Brazilian Sugarcane Production Systems.

The DAYCENT model is a process-based plant/soil ecosystem model that simulates trace gas fluxes as well as plant/soil carbon (C), nitrogen, and other ecosystem variables. It differs from its predecessor CENTURY by running on a daily instead of a monthly time step, with the added capacity to simulate water flow through soil layers as well as the flux of gases from soils such as nitrous oxide (N₂O), an important greenhouse gas. Brazilian sugarcane production is expanding due to growing demand for sugar and biofuels, and simulation models such as DAYCENT play an important role in understanding the ecosystem impacts of land use conversion into sugarcane as well as differences in management practices. While CENTURY has been developed to model soil C and yield impacts of Brazilian sugarcane expansion and production- including land use conversion into sugarcane from pasture and native vegetation as well as management practices such as burning versus green harvest- the DAYCENT model has had limited application in Brazilian sugarcane systems. We use soil C data from pairs of land conversion sites across major sugarcane producing regions in South Central Brazil, N₂O data from two years of continuous monitoring in different stages of a sugarcane crop, and N₂O data from a series of sugarcane management experiments (including a range of tillage treatments as well as different types and quantities of fertilizer application) to parameterize and validate the DAYCENT model. We compare DAYCENT and CENTURY model parameterization for sugarcane, as well as model performance simulating soil C changes with land use conversion.