Abstract
To examine whether crop climate modeling using data based on phonological stages is appropriate for identifying different climatic effects on corn yields, two phonological models and a model using monthly data are devised for portions of Illinois for the period 1951–80. Comparisons of thew models show that there are no significant differences among the three models for the area as a whole. However, geographical differences in the suitability of these models are observed. When only a limited number of variables are used, the phenological models perform better for a major part of the state compared to the model based on calendar month data. Therefore, a fourth model called the Parsimonious Model, using selected variables from one of the two phenological models, is presented. The variables used in the Parsimonious Model represent the major agroclimatic controls on corn. Parsimonious models for sample areas show that climate has different impacts on corn yield variability in northern versus southern Illinois. Yields in northern Illinois are found to be more sensitive to precipitation during early phenologic stages and in southern Illinois to temperatures during later phenologic stages.
