Late Season Corn Stalk Nitrate Test

A key to improving nitrogen management over time is having dependable feedback as to how well your nitrogen management plan is working. The information you obtain from the Late Season Corn Stalk Nitrate Test can be very useful for improving yield, optimizing profitability and making future management decisions.

Why Should I Test?

Nitrate testing provides good agronomic information regarding whether your current fertility program supplies an adequate amount of nitrogen, too little or excess. It’s also required by several NRCS (Natural Resources Conservation Service) Programs where funding is involved.

Taking the Sample

• Samples are taken 1-3 weeks after 80% kernel black layer has formed. Leaf sheaths should be removed and damaged or diseased stalks should be avoided.
• An 8” segment of stalk is removed beginning 6” above ground level (from 6” to 14” above ground). Be careful not to include any soil.
• 15 stalk samples are taken randomly in the field from healthy plants.

Preparing the Sample

• It is advisable to chop or shred the samples to allow them to dry before and during shipment.
• Ship in paper, not plastic bags.
• Refrigerate the sample if it cannot be dried or shipped immediately. Do not freeze.

What Will Lab Results Tell Me?

Interpretation of Stalk Nitrate Concentrations

Dairyland Laboratories will measure the nitrate in the section of stalk on a ppm basis. A low nitrate reading means that not enough nitrogen was available to the plant to reach full yield potential. A high nitrate reading means that excess nitrogen was applied, reducing profitability and jeopardizing the environment.
Based on the results of the nitrate tests and after considering the effects of weather during the growing season, decisions can be made to adjust the fertility program for subsequent years.

Reference Material  

NRCS Bulletin, WQL04
Cornstalk Testing to Evaluate Nitrogen Management, Iowa State University, PM 1584
The Basal Stalk Nitrogen Test for Corn, George Rehm, University of Minnesota