A GEOGRAPHIC ANALYSIS OF GRAIN CORN YIELD TRENDS IN ONTARIO USING A COMPUTERIZED LAND INFORMATION BASE

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Abstract
The geographic variability of grain corn yield trends in Ontario for the period 1961–1982, and the relative importance of nitrogen fertilizer, weather variability, technology and cropland expansion on these trends was investigated. Of particular interest was the difference in yield response among regions to the increased weather variability in the 1970s. After the effects of weather on yield were removed, linear and nonlinear as well as positive and negative technology (time) trends were observed, depending on the suitability of soils and climate for corn in each area. Yield increases resulting from technology improvements (assuming normal weather) averaged 2, 1 and 0.3% per year in the most suitable, intermediate and marginal areas, respectively. Grain corn yields were more closely related to weather variability than to nitrogen fertilizer sales or cropland expansion. Although N fertilizer increased coincidentally with yield in the 1960s, a low correlation (r = 0.16) over the whole 1965–1982 period indicated the likely importance of other factors on yield. Weather parameters related to temperature and precipitation explained 21–64% of the variation in yield in multiple linear regression analyses. Including time parameters (technology) in the regression improved the explained variance for most map units (R2 = 0.36–0.79). A decrease in yields and an increase in yield fluctuations observed in many areas in the mid-1970s appeared to be related to increased weather variability, the greatest effect of which was in the areas least suited to corn. Grain corn yields have continued to increase in some areas of Ontario while in other areas yields have plateaued or decreased marginally. This pattern is distributed geographically north and eastward from the most suited regions. Key words: Corn yield, weather variability, nitrogen fertilizer, cropland expansion, land information, data bases

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