| Over the past 30 years the behavior of crops, i.e., systems consisting of a community of plants, has been analyzed using computer simulation techniques. Models of crop growth and development consist of an array of mathematical equations that are, almost without exception, based on a combination of empirical relationships and physical/biochemical principles. The objective of this study was to evaluate the strengths and weaknesses of the model MAIS, a model of maize growth and development. A detailed description of the code is presented with emphasis on the physiology underlying the mathematical expressions used. The model is tested and evaluated, using the Mean Squared Deviation method (MSD), to meet the objective of finding the strength and weaknesses of the model by comparing simulated and actual results of various aspects of growth and development of maize grown in Southern Ontario. The critical issue in testing the 'validity' of the model is not necessarily the "fit" of the model to a given data set, but rather its capability to solve a conceptual problem and the validity of the model's hypotheses and logical structure. The continuous flow of research results that appears in the literature should be used to improve crop models and, in doing so, the interpretation and impact of the very results will be enhanced. The question what information is most limiting the utility of the model is not only important to the crop modeler, but also points to high impact areas of research. |
