Corn Stalk Nitrate Test - Key Insights for Nitrogen Management

By Blake Jackson

The corn stalk nitrate test (CSNT) serves as a valuable tool for evaluating nitrogen (N) management in corn fields, particularly those in their second or subsequent years after sod.

It identifies instances where N availability surpassed crop needs during the growing season, indicated by CSNT values exceeding 2000 ppm.

Consistent CSNT values above 3000 ppm over two or more years suggest potential for N management adjustments without compromising yield.

In 2024, a significant 47% of tested fields showed CSNT-N levels above 2000 ppm, with 37% surpassing 3000 ppm and 28% exceeding 5000 ppm. Conversely, 20% of samples indicated low CSNT-N levels.

While two years of CSNT data are generally recommended before altering management practices, a single year of data is sufficient when CSNT values exceed 5000 ppm.

Variations in CSNT distribution across years may reflect differences in growing season conditions. Notably, the percentage of samples with excessive CSNT-N from 2010 to 2024 correlated with total precipitation in May-June.

Drought conditions during these months often resulted in a higher percentage of fields with excessive CSNT. Despite some localized droughts, 2024 was generally classified as a normal growing season, though these localized droughts possibly increased the number of excessive CSNT results.

Within-field spatial variability is a critical consideration in New York. Accurate whole-field assessments necessitate either high-density sampling, equivalent to at least one stalk per acre, or targeted sampling based on yield zones, elevations, or soil management units.

Targeted within-field CSNT sampling is recommended as one of five end-of-season evaluation tools in the Adaptive Nitrogen Management for Field Crops in New York. Recent sampling may reflect this more targeted approach.

Interpreting CSNT results requires considering crop and manure management history, soil type, and growing conditions.

Factors such as weed and disease pressure, moisture availability, and oxygen levels in the root zone can significantly impact crop growth and N status. Therefore, conclusions regarding future N management should account for these variables.

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