More N is added for corn than any other nutrient in Minnesota. The right amount of N optimizes crop yield while minimizing loss of N to the environment. The wrong amount eats into profits and can send excess nitrogen into ground water. Figure 1 illustrates the significant impact the N rate has on crop yield, as well as its potential loss to ground water. Finding the right amount of fertilizer N to add for a crop means first estimating how much N is available from the soil and then adding fertilizer N to meet the crop's total N need. Because uncontrollable factors like precipitation and temperature affect the release of N from soil as well as the amount of N needed by a crop, the optimum amount of fertilizer N can change from location to location and from year to year. Continual studies measuring corn yield response to fertilizer N take these variations into account.
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Minnesota Water Research Digital Library