DNDC (DeNitrification-DeComposition) is a process based model of carbon and nitrogen biogeochemistry in agro-ecosystems. The model was developed by Professor Changsheng Li and colleagues at the University of New Hampshire, United States. The model was originally developed to simulate nitrous oxide (N2O) emissions from annual cropping systems in the United States (Li et al., 1992). Since its original development other researchers have modified the model to adapt it to other production systems, such as rice paddies, grazed pastures and forests, and many of these modifications have been incorporated into the latest versions of the DNDC model (Giltrap et al., 2010). Adaptation has frequently involved integration with other ecosystem models. The model can be used for simulating crop growth, soil temperature and moisture regimes, soil carbon dynamics, nitrogen leaching, and emissions of greenhouse and trace gases including nitrous oxide (N2O), nitric oxide (NO), dinitrogen (N2), ammonia (NH3), methane (CH4) and carbon dioxide (CO2).
In DNDC the primary drivers (climate, soil, vegetation and management) determine the soil environmental factors (temperature, moisture, pH, Eh and substrate concentration gradients). Biogeochemical processes of nitrification, denitrification and fermentation are represented as microbially mediated processes regulated by the soil environmental factors. The functional relationships were largely developed from experimental data in controlled environments. There are five interacting sub-models: thermal hydraulic; aerobic decomposition; denitrification; fermentation; and plant growth (including the effects of land management). The first three sub-models are described in Li et al. (1992) while Li et al. (1994) describes the plant growth and land management sub-models. A dynamic scheme describing soil redox potential evolution was added in DNDC for simulating fermentation processes (Li, 2000; 2007). The methods of simulating nitrous oxide, methane and ammonia are described in Li (2000; 2007). Model calculations are performed at a daily or hourly time step.
The DNDC model can be run in single site mode for crop rotations, or at regional scale using a GIS database to manage environmental and land management data, through a comprehensive graphical user interface which also displays summary model output. The interface also enables Monte-Carlo uncertainty analysis at site scale for the majority of input data. Uncertainty analysis at regional scale is limited to the Most Sensitive Factor method.DNDC has been extensively applied in China and India to study greenhouse gas emissions from rice and wheat systems. DNDC has been developed to study grain and pasture lands in Australia and New Zealand, and has been developed to study forest ecosystems in Europe and the United States. The model has been used as part of the European Union nitrogen biogeochemistry projects NOFRETETE and NitroEurope and is currently is being used for trace gas inventory and Best Management Practice studies at site, regional or continental scale.