Abstract. Nitrogen applied to the surface of the land for agricultural purposes represents a significant source of reactive nitrogen (N_r) that can be emitted as a gaseous N_r species, be denitrified to atmospheric nitrogen (N₂), run off during rain events or form plant-useable nitrogen in the soil. To investigate the magnitude, temporal variability and spatial heterogeneity of nitrogen pathways on a global scale from sources of animal manure and synthetic fertilizer, we developed a mechanistic parameterization of these pathways within a global terrestrial land model, the Community Land Model (CLM). In this first model version the parameterization emphasizes an explicit climate-dependent approach while using highly simplified representations of agricultural practices, including manure management and fertilizer application. The climate-dependent approach explicitly simulates the relationship between meteorological variables and biogeochemical processes to calculate the volatilization of ammonia (NH₃), nitrification and runoff of N_r following manure or synthetic fertilizer application. For the year 2000, approximately 125 Tg N yr⁻¹ is applied as manure and 62 Tg N yr⁻¹ is applied as synthetic fertilizer. We estimate the resulting global NH₃ emissions are 21 Tg N yr⁻¹ from manure (17 % of manure production) and 12 Tg N yr⁻¹ from fertilizer (19 % of fertilizer application); reactive nitrogen runoff during rain events is calculated as 11 Tg N yr⁻¹ from manure and 5 Tg N yr⁻¹ from fertilizer. The remaining nitrogen from manure (93 Tg N yr⁻¹) and synthetic fertilizer (45 Tg N yr⁻¹) is captured by the canopy or transferred to the soil nitrogen pools. The parameterization was implemented in the CLM from 1850 to 2000 using a transient simulation which predicted that, even though absolute values of all nitrogen pathways are increasing with increased manure and synthetic fertilizer application, partitioning of nitrogen to NH₃ emissions from manure is increasing on a percentage basis, from 14 % of nitrogen applied in 1850 (3 Tg NH₃ yr⁻¹) to 17 % of nitrogen applied in 2000 (21 Tg NH₃ yr⁻¹). Under current manure and synthetic fertilizer application rates we find a global sensitivity of an additional 1 Tg NH₃ (approximately 3 % of manure and fertilizer) emitted per year per °C of warming. While the model confirms earlier estimates of nitrogen fluxes made in a range of studies, its key purpose is to provide a theoretical framework that can be employed within a biogeochemical model, that can explicitly respond to climate and that can evolve and improve with further observation.