Let nitrate stalk tests guide your N plans

G & K Concepts, Harlan, isn’t the only firm that believes in the value of stalk nitrate tests. Here’s what others say about the potential value of testing stalk samples.

“It works well as a measure of your success or failure in nitrogen management for the previous year,” says Andy Awald, Farm Fertilizers & Seeds, Hamlet. “You can tell whether plants had too much, too little or just the right amount of nitrogen.”

Plants generally take up as much N as is available and store it in the stalk, the Indiana Certified Crop Adviser notes.

Key Points

Stalk nitrate test results can be important report card on the year’s N program.

The environmental effect from year to year can be huge.

Consider tweaking fields with maximum yields and high stalk nitrate values.

Low nitrate levels in the stalk likely indicate a deficiency and that the crop could have used more nitrogen. The plant may have had to cannibalize N from the stalk to finish grain fill.

Too much residual N in the sample says that the plant had “luxury consumption” of N, which is detrimental to your pocketbook.

“It’s a good tool to try to tweak your N program when the cost of N is high,” Awald notes. “Bear in mind, though, that the environment will affect N usage by the plant. Multiple years’ worth of results will be more valuable than a single year’s results.”

Weather factor

Steve Gauck, CCA with Beck’s Seeds, Westport, agrees stalk nitrate testing is a great way to look at how your N program worked. But he also emphasizes the environmental factor.

“The amount of N available this year was greatly affected by early rains,” he notes. “This gives you a chance to see if you need to make adjustments to how you apply nitrogen.”

David Taylor, CCA and agronomist for Harvest Land Co-op, Portland, points customers toward a Purdue University Extension publication. He believes AY-322-W gives helpful tips on what can be learned from stalk nitrate testing.

Helpful hints

According to the data collected by Purdue for the publication, the stalk nitrate test can identify corn that produces less than maximum yield because of nitrogen stress, Taylor observes. This can happen if the results show less than 700 parts per million of nitrate once the lab analyzes stalk samples.

However, low stalk nitrate values don’t always mean low yield. Maximum yield can be obtained in some cases when the test values are below 250 parts per million.

The test identifies areas in the field where excessive soil nitrogen exists, Taylor says. These areas are where maximum yields were achieved, and test values were still above 2,000 parts per million. Such test results might be especially helpful if manure was applied and the farmer earlier questioned whether there was an extra need for nitrogen beyond that supplied by the manure or not.

Taylor urges caution. “When N programs are being fine-tuned, they should be changed in a manner that will not have large impacts on final yield,” he concludes.


Future information: These stalk samples bagged to dry may not look important to you, but many agronomists feel they hold key information to help fine-tune N programs.

This article published in the September, 2011 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.