Oct. 16, 2014

Late season stalk nitrate tests are used to assess the nitrogen status of corn plants at physiological maturity. This year may provide interesting information since we had greater than average rainfall for most of the eastern part of the state. (See resources below on how to take and interpret these samples.)

Reports are that nitrogen leaching may have been widespread, and some nitrogen that was intended to go on in irrigation water, may not have been applied. From my experience and sampling in research plots, stalk nitrate tests have to be viewed with other knowledge about the field and the cultural practices.

I have seen where late season nitrogen was in the plant stalks, but did not affect yield. I have also seen, mostly on sandy ground, where low stalk nitrates (below 700 ppm) did not indicate N deficiency, but effective utilization of all the nitrogen in the plant.

The best use of this test is to compare different treatments, such as a strip trial where extra nitrogen was applied sidedress. The information from the stalk nitrate test is better interpreted with yield data.

Additional Resources

• Does Your Current Corn Nitrogen Strategy Deserve an A or a D? Use Fall Corn Stalk Tests to Guide Nitrogen Rates
   
• Soil Management section of CropWatch, including Nebraska-specific recommendations and resources
   
• Fertilizer Suggestions for Corn (UNL EC117)
   
• Daily Soil Temperature Updates. If applying nitrogen in the fall, deplay applications until average soil temperatures are consistently below 50"F.

Charles Shapiro, CPAg, ExtensionSoil Scientist
Haskell Ag Lab