corn field

Now is the time to evaluate your nitrogen management using the corn stalk nitrate test.

For farmers, nitrogen can be challenging to manage because of how mobile it can be both within the soil and the atmosphere. To determine if nitrogen applications were properly administered, a corn stalk nitrate test can be done to assist in future applications.

Nitrogen is the macronutrient that corn needs to grow to its fullest potential, whether that is to put on numerous large leaves for silage or multiple rows of kernels for grain.

Extension agronomist Mason Tate says nitrogen can be challenging to manage because of how mobile it can be both within the soil and the atmosphere. Factors that influence the behavior of nitrogen include the source, placement, timing of application, and weather.

This year, large amounts of rainfall were recorded in some parts of the state, so the potential for nitrate leaching and denitrification increased.

Some regions of the state had a prolonged dry spell in the spring, which can promote volatilization losses of ammonia.

In a time when materials and production costs are high, it is important for producers to manage their nitrogen carefully. Conducting a corn stalk nitrate test, or CSNT, allows producers to identify cornfields that are low, optimal or excessive in their availability of nitrogen to the corn crop over the growing season. The best interpretation of the CSNT results and how to improve your nitrogen management practices can be achieved when you can relate your nitrogen management practices to your CSNT results. This includes considering what the previous crop was (legumes such as alfalfa, clover and soybeans provide a nitrogen credit), what form, rate, timing and placement of nitrogen fertilizer or manure was used, the manure history in the past five years, and whether your actual yield compared to your typical yield goal.

The earliest a producer can conduct a CSNT is at one-quarter milk line, which can be determined when the ear of corn is broken in two. The milk line is the border between the milk and starch layers that can be seen when looking at the broken half with the tip of the ear.

The latest a producer can conduct a test is three weeks after black layer (physiological maturity).

Ten representative plant samples need to be taken within the cornfield. Choose healthy disease-free samples to include in your CSNT. An 8-inch stalk sample needs to be taken, beginning 6 inches above the soil surface.

Once samples have been collected, the 10 stalks need to be cut into 2-inch sections. Place samples in a paper bag to be mailed to the Penn State Agricultural Analytical Services Laboratory, 111 Ag Analytical Services Lab, University Park, PA 16802.

If samples are being held over the weekend, place them in a paper bag and put in a refrigerator. Do not freeze the samples.

For instructions on how to submit a CSNT test, visit the Agricultural Analytical Services Laboratory. Join us Sept. 21, 8:30 a.m. to 3:30 p.m., at the Penn State Southeast Research and Extension Center, 1446 Auction Road, Manheim, Pennsylvania.

At 9:30 a.m., Charlie White will discuss assessing nitrogen management in corn with end-of-season testing.

Leon Ressler is a Penn State Extension educator based in Lancaster County, Pennsylvania.

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