Nitrogen is essential to corn production, but both inadequate and excessive nitrogen can create questions at the end of the growing season. Elevated nitrate levels may also remain in harvested crops and become a safety concern when those crops are used as livestock feed.

In its July 2026 edition of The Lab Scoop, Waters Agricultural Laboratories highlighted the value of end-of-season corn stalk nitrate testing and the risks associated with nitrate toxicity in livestock feed.

These are important topics for producers, but they may also become relevant during agricultural claim investigations involving crop performance, fertilizer application, feed quality, livestock illness, or unexpected livestock deaths.

Evaluating Nitrogen Management in Corn

An end-of-season corn stalk nitrate test measures nitrate remaining in the lower stalk after the crop reaches maturity.

The results can help indicate whether nitrogen availability during the growing season was likely deficient, generally appropriate, or higher than the crop needed. This information may help producers evaluate whether their nitrogen-management practices supported the intended yield.

Waters recommends collecting samples near the end of the season, generally after black layer development. Because laboratory results depend on the quality of the sample, collection should represent the field area being evaluated and avoid plants affected by unrelated damage or disease.

The test does not answer every question about crop performance. Weather, soil conditions, plant health, application timing, and other factors may also affect the final crop. However, the results can provide another piece of objective information when the adequacy or use of nitrogen is being reviewed.

When Nitrates Become a Livestock Feed Risk

Plants normally absorb nitrate from the soil and convert it into compounds used for growth. When plants are stressed or receive more nitrogen than they can use, nitrate may accumulate in the plant.

That buildup can become dangerous when affected hay, silage, corn, or forage is fed to livestock. Inside the animal, nitrate can be converted into nitrite, which interferes with the blood’s ability to carry oxygen.

Signs may include weakness, tremors, rapid or difficult breathing, disorientation, difficulty standing, and collapse. In severe cases, animals may be found deceased before a problem with the feed is recognized.

When elevated nitrate levels are suspected, testing a representative feed sample can help determine whether nitrate exposure should be considered as part of the investigation. Veterinary findings remain important when livestock illness or death is involved.

Why This Matters in Agricultural Claims

Crop and livestock claims often involve several possible causes. Laboratory testing does not establish coverage or determine liability by itself, but it can help document conditions that may have contributed to the loss.

Depending on the claim, useful information may include:

• Laboratory results from crop or feed samples
• Fertilizer products, rates, timing, and application records
• Weather and growing conditions
• Evidence of drought, disease, hail, insect damage, or other plant stress
• The source, storage, and feeding history of the forage
• The timing of livestock symptoms or deaths
• Veterinary reports, treatment records, and necropsy findings

Sampling should be completed as early as practical and according to the laboratory’s instructions. The identity and location of each sample should also be clearly documented so the results can be connected to the field, feed source, or loss being investigated.

Objective Information Supports Better Investigations

Nitrate concerns can begin with crop management in the field and continue after harvest when the crop becomes livestock feed.

For producers, testing can support safer feeding and better nitrogen decisions. For agricultural claims professionals, it may provide valuable evidence that helps clarify the conditions surrounding a loss and guides the investigation toward the appropriate experts and next steps.

Source: Information adapted from the July 2026 edition of The Lab Scoop by Waters Agricultural Laboratories. For technical sampling instructions and testing recommendations, contact Waters Agricultural Laboratories directly.