Modelling agriculture and the environment: Crop production and diffuse pollution

Simulation modelling in the agricultural sector, with particular reference to the relations between agricultural activities and the environment is reviewed. The modelling or growth and productivity of crops and the simulation of the environmental fate of nutrients and pesticides are considered. The origin, development and general characteristics of the models are defined with the aim of identifying their potential usefulness in dealing with major environmental problems associated with agricultural activities. Current implementations of models for studying non-point source pollutants in agriculture are presented, according to the spatial scale on which they occur. The potentials and prospects for future application are discussed in the light of problems due to the proliferation of proposed methods, the complexity of the phenomena in question, evaluation of the quality of data and results, treatment of spatial variability, and the peculiarity of applications on a territorial scale, for decision-making or planning purposes. The structure and components of future models aimed at dealing comprehensively with agro-environmental problems are proposed. It is suggested that an international model bank should be established to allow the exchange of multidisciplinary modules and models, documented and classified ill terms of their characteristics and ranges oi applicability. These models should also be capable of working in incomplete structures, substituting marginal sub-models with fixed input parameters and limiting the set of outputs. Results of modular simulations should keep track of the combination of assumptions, approaches and limits of the modules connected to the engine, by retreiving information stored in the model bank.