End of season nitrate test examines nitrogen use in corn crop

 

Bill Meyer

 

DYERSVILLE — The end-of-season cornstalk nitrate test measures how well corn plants have used nitrogen (N) and can be an excellent way to determine if a corn crop had adequate nitrogen late in the growing season.  The test measures nitrate concentrations in the lower portion of the cornstalks at the end of the growing season.

As producers plan for the fall harvest, they can use the EOS cornstalk nitrate test to help make crop management decisions as well as analyze their financial bottom line.

Producers in the North Fork Maquoketa and Hewitt Creek watersheds near Dyersville have the chance to get cornstalk nitrate sampling done through the watersheds’ incentive programs.

Bill Meyer of Dyersville will again collect samples and send them to the lab for watershed participants who choose to use the program.  Signup is at the watershed council meetings held in August.

The basis of the test is straightforward.  If a corn plant is suffering from inadequate N availability, it removes N from the lower cornstalks and leaves during grain filling. If the plant has more N than needed for maximum yields, nitrate accumulates in the lower stalks at the end of the season. Producers can use this information to determine if their corn crop had adequate N late in the growing season.

Taking the samples is straightforward.  Fifteen eight-inch sections (the stalk is cut at six and 14 inches above the soil for each stalk sample) of cornstalks are taken one to three weeks after kernel black layer has formed, and sent to an appropriate laboratory to be sampled for nitrate content.

For participating producers in the two watersheds, the test results are returned both to the producer and to the staff at the Iowa State University Extension Performance-based watershed projects in Fayette.  The staff use the results to construct a watershed-wide snapshot – without producer names – for discussion at the watershed council meetings.

Test results are easy to interpret.  If the test results are less than 700 parts per million (ppm), N levels may have been inadequate. If they are above 2,000 ppm, N levels were probably more than needed. Levels between 700-2,000 ppm indicate optimal N availability to the crop.  When used over a number of years, the stalk nitrate test can help refine N management.

Meyer, who has a degree in crop science from the University of Illinois, started taking cornstalk samples for the Hewitt Creek watershed in 2005.  He said it was a natural move to assist with the North Fork watershed council program.

Project cooperators are charged for the sampling, $60 for the first two and then $25 for each additional sample, part of which is reimbursed if they are participating in the watershed incentive program.

Meyer says he needs to know the cropping history of the field to be sampled and whether the corn will be harvested as silage or shelled corn.  He also estimates yield while in the field collecting stalk samples.

North Fork Maquoketa watershed producers who are interested in trying this test may contact Meyer, David Krapfl, North Fork council chairman, Jeff Pape, Hewitt council chairman, or the Iowa State University Extension Performance-based Watershed Projects office, 563 425-3233.

For more information on collecting cornstalk NO3 samples, click on:

stalk NO3 sampling