The effect of cattle slurry on the field nitrogen cycle was modeled with Swedish CoupModel (former SOIL-SOILN). Soil physical characteristics were estimated according to soil texture. The amount of soil carbon and nitrogen were estimated by fitting the nitrogen uptake of unfertilized barley crops on nitrogen mineralisation from soil organic matter. Using these soil parameters, the model was used to give estimations of the effects of different slurry application times and amounts on nitrogen uptake by crop, soil mineral nitrogen contents and nitrogen leaching. Ammonia volatilization from slurry was estimated by an equation based on air temperature. The modeled nitrogen uptakes and soil mineral nitrogen contents were higher than measured except in late spring applications. If 30 50 % of slurry nitrogen applied in autumn or early spring was taken out of the system, measured and modeled results agreed reasonably. The main reasons for the need of the correction were probably inaccuracies in the estimations of ammonia volatilization, low modeled denitrification and low modeled nitrogen immobilisation to microbes in the decomposition of slurry. According to the comparison between modeled and measured soil mineral nitrogen contents it was clear that the model did not calculate nitrogen processes in low temperatures with good precision. When comparing nitrogen leaching of different application times the model estimated autumn application of slurry to increase nitrogen leaching 4 12 kg/ha.