Late Season Cornstalk Nitrate Test Sampling Procedure


Stalk sampling can be done anytime between about the ¼ milkline stage of the grain and up to 3 weeks after the grain forms a blacklayer. Depending on planting date, location, etc., this sampling window usually is from about the later part of August until the later part of October. If any of your fields will be taken for silage, you will need to sample before the silage harvest (often about ½ milkline stage).


Samples will be 8-inch long sections of cornstalk (subsequently cut into two inch long segments) taken 6 inches above the ground. A stalk section from each of 10 representative plants would be a good sample size for a field.


A pair of sharp hand-pruning shears are probably the best tool for taking stalk samples. Lopping shears can be used (especially for extra thick stalks), but usually aren't as convenient to carry around a field. A machete or corn knife will work, but not as nicely as shears. You can use a tape rule, yard stick or marked rod for the measurements. One possible shortcut measuring system is to mark your pant leg 14 inches high and use this to measure for your first cut. After discarding the top of the plant, then use your pruning shears which may be about 8 inches long to measure for your second cut. This should result in an 8-inch stalk sample taken and a 6-inch stalk stubble left in the field. To facilitate processing your stalk samples, please cut each of your stalk sections into approximately two inch long segments before you send them to the lab.

Sample Handling

If possible, dry the sample immediately or mail to the lab as soon as possible after collection. If there is more than a day between sampling and mailing, store sample in paper bag and refrigerate (don't freeze). To prevent molding, do not store sample in plastic bag or other non-breathable container for an extended period of time. Routine turn-around is ten to fifteen business days from the sample arriving at the laboratory.  Send the sample, completed submission form and payment ($12.00 per sample) to the Agricultural Analytical Services Laboratory in the mailing envelope provided. Sample may be placed directly in mailing envelope. Submission form and check should be packaged separately in zip lock bag to avoid contact with moist samples. If submitting multiple samples, you may package together in your own shipping container and mail to:

The Pennsylvania State University
111 Ag Analytical Srvcs Lab
University Park, PA 16802-1114