Corn yield response to N fertilizer varies from year-to-year owing to weather. Optimal N rates depend on the yield response, and also vary with the price ratio between fertilizer and corn. In a trial in Elora, Ontario, optimal N rates over six years varied more than three times as much due to differences in weather as compared to differences in price ratio. While small profit gains can be achieved by adjusting N rates for price ratio, there is much more potential profitability and environmental benefit to be gained in better adapting N management to weather.
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