Sanjay Gami¹, Juan Carlos Ramos Tanchez¹, Mike Reuter², and Quirine M. Ketterings¹
¹Cornell University Nutrient Management Spear Program (NMSP) and ²Dairy One
Introduction
The corn stalk nitrate test (CSNT) is an end-of-season evaluation tool for N management for corn fields in the 2nd or more years after a sod. It allows for identification of situations where more N was available during the growing season than the crop needed (CSNT>2000 ppm). Results can vary from year to year but where CSNT values exceed 3000 ppm for two or more years, it is highly likely that N management changes can be made without impacting yield.
Findings 2010-2024
In 2024, 47% of all tested fields had CSNT-N greater than 2000 ppm, while 37% were over 3000 ppm and 28% exceeded 5000 ppm (Table 1). In contrast, 20% of the 2024 samples were low in CSNT-N. Two years of CSNT monitoring is recommended before making management changes unless CSNT’s exceed 5000 ppm, in which case one year of data is sufficient.
Some of the variability in CSNT distribution over the years may be reflect differences in growing season (Figure 1). The percentage of samples testing excessive in CSNT-N across 2010-2024 was most correlated with the total precipitation in May-June with droughts in those months translating to a greater percentage of fields testing excessive. The year 2024 was classified as normal based on these criteria although some areas experienced drought conditions for parts of the season, possibly contributing to a higher percentage of stalks testing excessive in CSNT.
Within-field spatial variability can be considerable in New York, requiring (1) high density sampling (equivalent of 1 stalk per acre at a minimum) for accurate assessment of whole fields, or (2) targeted sampling based on yield zones, elevations, or soil management units. The Adaptive Nitrogen Management for Field Crops in New York lists targeted within-field CSNT sampling as one of five end-of-season evaluation tools. Samples received in more recent years may also reflect more targeted field sampling.
Because crop and manure management history, soil type and growing conditions all impact CSNT results, conclusions about future N management should consider the events of the growing season. This includes weed and disease pressure, lack of moisture in the root zone in drought years, lack of oxygen in the root zone in wet years, and any other stress factor that can impact crop growth and N status.
Relevant References
• Instructions for CSNT Sampling: http://nmsp.cals.cornell.edu/publications/StalkNtest2016.pdf.
•. Agronomy Factsheets #31: Corn Stalk Nitrate Test (CSNT); #63: Fine-Tuning Nitrogen Management for Corn; and #72: Taking a Corn Stalk Nitrate Test Sample after Corn Silage Harvest. http://nmsp.cals.cornell.edu/guidelines/factsheets.html.
•. Adaptive Nitrogen Management for Field Crops in New York (2025): http://nmsp.cals.cornell.edu/publications/extension/AdaptiveNitrogenManagement2025.pdf.
Acknowledgments
We thank the farmers and farm consultants that sampled their fields for CSNT over the years.
For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.
