Fall 2011 end-of-season corn stalk nitrate test can fine-tune your 2012 nitrogen program

The corn stalk nitrate test taken in the fall is an “after-the-fact” diagnostic tool that can determine if excess nitrogen was applied to corn. Use the results now to fine-tune your nitrogen management program.

The nitrogen (N03-N) concentration in the lower portion of the corn stalk just after black layer formation in the fall is a good indicator of nitrogen (N) status of the corn crop throughout the growing season. This information must be carried forward into the next growing season to achieve the real benefit of the test.

Pull out last fall’s (2011) test results. For most conditions prevailing in the Corn Belt, stalk N03-N concentrations between 700 and 2,000 ppm have been accepted as the critical optimal range. For more information, see the article End of season corn stalk nitrate test from August 2011. Lower than 700 ppm suggests more N may be needed to maximize yields. Concentrations higher than 2,000 ppm suggest that corn had more N than needed and dollars could be saved by reducing the N fertilizer rate.

As we approach the time for sidedressing N fertilizer, we are entering the last “window of opportunity” to make adjustments to the N rate. Use last fall’s corn stalk nitrate test as a starting point to determine the appropriate adjustments to your N practices.

Another diagnostic test, particularly on fields that have manure or alfalfa history, is the pre-sidedress soil nitrate test (PSNT). For information on how to best use the PSNT, see the article Pre-sidedress soil nitrate test will save money on nitrogen fertilizer. This test will indicate the potential for soil N mineralization during the season.

The investments made in both tissue and soil diagnostic tests and the correct interpretation and implementation of the results can pay dividends as improved corn yields and reduced fertilizer dollars.

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