Low hanging fruit?

Low hanging fruit?

Nitrogen rate management (MRTN) is the low-hanging fruit of the Iowa Nutrient Reduction Strategy, a win-win for profitability and the environment.  On closer inspection, that fruit is even juicier than we thought; but harder to reach.   Here’s the paradox of nutrient management that the general public fails to grasp.  We don’t know with any certainty at application time how much nitrogen the corn crop will need or how much nitrogen will be left in the soil come July when the crop starts maturing.  Corn stalk nitrogen tests and split applications can improve the accuracy of the guess, but farmers still have to guess.  If they guess too low, they lose income.  So most farmers err on the high side, which means that (all else being equal) more nitrogen will end up in our streams. Figure by John Sawyer at ISU.  The economically optimum nitrogen rate varies by year, even on the same field. We may not know what’s the right amount of nitrogen...
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