The University of Missouri Stalk Nitrate Challenge

Did you do a good job predicting nitrogen need for your corn crop last spring? Did you over apply? Under apply? Or get your rates just right? The stalk nitrate test is a powerful tool for assessing the fertilizer nitrogen decisions in a corn field.

Research from Iowa and other states has calibrated nitrate concentration in the corn stalk with the nitrogen status of the harvested corn crop. Nitrate concentrations above 2000 parts per million are indicative of a crop that had excess nitrogen; nitrate concentrations below 700 parts per million are indicative of plants that had marginal nitrogen supply (250-700 parts per million) or were clearly nitrogen deficient (less than 250 parts per million).

How to sample fields

  • The window of opportunity for collecting samples is from ΒΌ milk stage to up to three weeks after black layer formation.
  • Use a set of hand shears or loppers to remove an eight-inch segment of corn stalk from the corn plant. The top cut should be 14 inches above the ground; the bottom cut six inches above the ground.
  • Get a segment from at least 15 randomly selected plants from the field or subfield you are sampling.
  • Place the samples in a paper bag for shipping to the lab for analysis. Do not freeze the sample. Samples held more than 24 hours before shipping should be refrigerated.
  • Penn State University has a good video on "Using the Stalk Nitrate Test". We recommend 15 stalks per field and do not require chopping the stalks into 2-inch sections.
  • A complete description of the test and its interpretation is available in the Iowa State Extension Publication (#1584) "Cornstalk testing to evaluate nitrogen management."

Participating in the Missouri Stalk Nitrate Challenge

  • My program is working with the University of Missouri Soil Testing Laboratory to promote use of this test in Missouri.
  • Typical analysis cost for the test is $12 per sample. We will analyze at the MU lab up to 10 samples from any Missouri farm at no cost if you submit the requested information on the following form when you submitted sample.
  • You must include a completed data form with each sumbitted sample. Please print this pdf form, fill it out and submit one form per sample.
  • Please mail samples to Attention Stalk Nitrate Challenge, University of Missouri Soil Testing Lab, 23 Mumford Hall, Columbia, MO 65211 or MU Delta Regional Soil Testing Lab, 147 State Hwy T, Portageville. MO 63873.

If you have any questions about this program please contact John Lory by email or at 573-884-7815.