The Canadian Land Surface Scheme (CLASS) has been coupled with carbon (C) and more recently nitrogen (N) modules to form a coupled carbon and nitrogen version of the model (CN-CLASS). In CN-CLASS, stomatal conductance and carbon assimilation are sensitive to leaf nitrogen content through the Rubisco enzyme. Nitrogen pools in the leaf, root and soil are represented, as are biological fixation, deposition, fertilization, mineralization, nitrification, root uptake, dentrification and leaching. This study presents four season-long runs of CN-CLASS at the NCC Research Farm near Ottawa, Ontario, representing both C3 and C4 photosynthesis; soybeans were planted in 1999 (C3), corn in 2000 and 2002 (C4), and spring wheat in 2001 (C3). CN-CLASS was forced in column mode (i.e. not coupled to an atmospheric model) using locally observed meteorological data with a 30 minute time-step. The performance of CN-CLASS is assessed through comparisons of observed and modelled energy and carbon fluxes, and the sensitivity of the output to uncertainty in model parameters is examined.