To Monitor The Nitrogen Status Of Your Corn Crop

On September 26, 2019

To Monitor The Nitrogen Status Of Your Corn Crop

In a wet year like 2019, there are many questions about how nitrogen fertility programs held up.  

Extension Agronomist Charlie White explains corn stalk nitrate testing can give you a glimpse into whether your corn ran out of N, had just enough N, or whether N applications were excessive.

Nitrogen (N) management is an adaptive process- you start out each season with a game plan for N applications in your crops, but as the season develops you have to decide whether to make adjustments or stay the course.  At the end of the season, it can be helpful to know, did the N management decisions you made this year result in just the right amount of N supply to corn, or did you apply too little or too much?  The late-season corn stalk nitrate test can provide this type of feedback on your N management program each year. 

The corn stalk nitrate test works by measuring the nitrate concentration in the lower part of the corn stalk.  This is an indication of how much of the nitrate taken up by the plant was used to build useful molecules for the plant, such as proteins or chlorophyll.  High levels of nitrate in the stalk at the end of the season indicate that the N supply to the crop throughout the season was excessive and the plant had access to more nitrogen than was actually needed.  Very low levels of stalk nitrate indicate that the crop may have run out of N, causing a yield loss.  Optimal levels of nitrate remaining in the stalk, which Penn State interprets as 700 to 2,000 ppm N, indicate that the crop had just the right amount of N available to maintain optimal growth and yield.

Detailed instructions for collecting a sample from the field for the corn stalk nitrate test are described in this fact sheet: Briefly, samples can be collected anytime between the ¼ milkline stage and 3 weeks after black layer formation.  From each plant, cut out the section of stalk starting at 6 inches above the ground and extending another 8 inches up (in other words, the section from 6 to 14 inches above the ground).  Collect stalk samples from 10 randomly selected representative plants per field.  Stalk segments should be further cut into 1- to 2-inch long segments to facilitate drying.  Place the samples in a paper bag and send to the lab for analysis as soon as possible.  

The current cost of a stalk nitrate test at the Penn State Agricultural Analytical Services lab is $12.  If a stalk nitrate test was collected from a 6 acre field, the analytical cost would only be $2/ac.  It is easy to see how the information gained, such as knowing whether you could potentially cut back on N fertilizer applications, or whether yield could be increased by increasing N fertilizer rates, would quickly pay for the cost of the analysis.  If the results show you achieved optimal N management for the year, it can build your confidence in continuing with the N management decisions that led to this success.  Without any feedback on how your N management decisions performed this year, N management will continue to remain a guessing game, potentially resulting in costly mistakes such as applying more N than is needed or losing yield due to N shortages.

To Get Your Household Well Tested

Have you ever had the drinking water from your well, spring or cistern tested for lead and other health-related pollutants? If not, here is your chance if you live in Lancaster County. 

Penn State Extension has received funding from the Rural Community Assistance Partnership (RCAP) and the U.S. Environmental Protection Agency to provide no-cost drinking water testing to a limited number of homeowners in Lancaster County using private water wells, springs or cisterns. The testing is for private water supplies that are actively being used for drinking water in the household or rental unit. Camps or seasonal households that are not continuously used are not eligible for this program. The commercial value of this water testing would be $125. 

This testing is limited to the first 45 households using a private well, spring or cistern that register online at or by calling Penn State Extension toll-free at 877-345-0691. Once you register, you can pick up your drinking water test kit at the Penn State Extension office in Lancaster County in the Farm & Home Center – 1383 Arcadia Road, Room 140, Lancaster, PA 17601. Instructions on how to collect the water sample are included in the kit. 

The kits must be dropped off at the Extension office between 8:30 AM and noon (12:00 PM) on either September 30 or October 14 (the exact drop-off date will be provided in your test kit). 

Individual water samples will be analyzed for numerous drinking water parameters including total coliform bacteria, E. coli bacteria, pH, total dissolved solids, hardness, alkalinity, corrosivity, nitrate, arsenic, copper and lead. Results of your testing will be available during two separate one-hour workshops to be held at 2:00 PM or 6:00 PM on November 7 at the Penn State Extension office (1383 Arcadia Road, Lancaster). You will be asked to attend one of these workshops to get your water test results. A brief 30-minute presentation will also be given including professional interpretation of your results and information on how to solve drinking water problems. 

If you have any questions about this no-cost testing program contact the Lancaster Extension Office at 717-394-6851 or .

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