In the Netherlands the Institute for Soil Fertility Research plays a major role in soil biological, soil physical and plant nutritional research on the availability of nitrogen to crops. Main subjects of research are nitrogen turnover in the crop-soil ecosystem through biological transformations, nitrogen transport through the soil and nitrogen losses by leaching, denitrification and volatilization, and nitrogen use efficiency of various crops and cropping systems. The current knowledge in the different fields of research is integrated in simulation models. Simulation models not only make it possible to summarize and structure knowledge, but also, after verification, to extra- late the knowledge to situations different from the situations that have actually been studied. Such research is also carried out in other European and non-European countries. To compare the various simulation models currently in use, a workshop was organized by the Institute for Soil Fertility Research on 5-6 June 1990 on the occasion of its centennial. The title of the workshop was 'Nitrogen turnover in the soil-crop:: cosystem: modelling of biological transformations, transport of nitrogen and nitrogen use efficiency'. The 40 Jarticipants, who came from Canada and various European countries, were requested to run their model with data Jrovided by the Institute prior to the workshop. Data from 18 cases were made available to the participants: three ocations, three treatments, and two seasons.

Nitrogen turnover in the soil-crop system; comparison of fourteen simulation models.- NQuantitative aspects of nitrogen nutrition in crops.- Modelling of the nitrogen cycle in farm land areas.- Nitrate leaching and soil moisture prediction with the LEACHM model.- Nitrate leaching and soil moisture prediction with the LEACHM model.- Some results of nitrogen simulations with the model ANIMO.- The distribution of water and nitrogen in the soil-crop system: a simulation study with validation from a winter wheat field trial.- Modelling water flow, nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential.- Modelling water flow, nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential.- Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model DAISY.- Simulation of the nitrogen balance in the soil and a winter wheat crop.- Modelling nitrogen dynamics in a plant-soil system with a simple model for advisory purposes.- Simulation of nitrogen in soil and winter wheat crops: modelling nitrogen turnover through organic matter.- Simulation of nitrogen in soil and winter wheat crops: modelling nitrogen turnover through organic matter.- Simulation of nitrogen in soil and winter wheat crops: a management model that makes the best use of limited information.- Modelling water flow, nitrogen uptake and production for wheat.- WHNSIM - a soil nitrogen simulation model for Southern Germany.- A comparison of the performance of N simulation models in the prediction of Nmin on farmers' fields in the spring.- Response of wheat to nitrogen fertilization, a data set to validate simulation models for nitrogen dynamics in crop and soil.- List of participants.