Should We Be Concerned About Nitrates in Corn Silage for 2023?

BY Dairyland Seed Agronomy Team

2023 Silage In Season Nutrient Management

The spoiler: We should not be any more concerned about nitrates in corn silage than any other year. Drought can increase nitrate concerns, but the timing of the drought in 2023 should leave us in the clear.

There are two primary causes of high nitrate accumulation in corn silage:

The drought scenario: Nitrate uptake from the soil will spike (if available in the soil) with rainfall that follows a dry period. This nitrate accumulates in the stalk and leaves for two to three days until it is put to work in the form of amino acids by the plant’s physiological engines. A silage crop harvested before this conversion can have high nitrate levels. In most cases, July and early August of 2023 have given us adequate rainfall to moderate the flow of nitrates into the plant over a wider timeframe, thus minimizing or eliminating this risk.
Vegetative growth stage silage harvest: Late planted corn or sorghum is a great option for generating tonnage. If these fields are underdeveloped to the point of not making grain, nitrates can be high in the stalk and leaves. This is exaggerated in frost-killing events. This is a very realistic scenario in 2023, where emergence issues delayed crop establishment early in the year.

If we are concerned about high nitrate levels in feedstocks, the solutions are simple. A big part of that is lab testing for nitrates. It is fast and easy to submit a sample and interpret results, so there is no excuse. There are two ways to solve this problem: fermentation and dilution.

Let the feed ferment for three to four weeks in storage. Fermentation cuts nitrate levels approximately in half, which usually solves the problem. Testing at harvest, and as you begin feeding, is a good idea. Avoid feeding green-chopped forage when you suspect high nitrates.
If feed is testing high, manage dry matter intake to regulate nitrate exposure. The total ration should be 900 ppm NO₃-N or less. Additionally, confirm that water sources are low nitrate. University recommendations are generally aligned but do vary slightly. Below are the dairy cattle guidelines from Penn State University, which are typically more restrictive than beef recommendations.

Penn State guidelines for feeding forages with high nitrate levels to dairy cattle. Link here
Nitrate Nitrogen (NO₃-N) (ppm dry matter basis)	Recommendations
<1,000	Safe under most conditions.
1,000-1,700	Gradually introduce to ration. Test all feeds and water. Dilute to 900 ppm NO₃-N in total ration dry matter.
1,700-2,300	Possible acute toxicity. Feed in a balanced ration with concentrate. Test all feeds and water. Dilute to 900 ppm NO₃-N in total ration dry matter.
>2,300	Do not feed to dairy cattle. Some universities still recommend dilution of feedstock testing as high as 4,000 ppm NO₃-N back to 900 ppm for beef cattle. These sources should not make up more than ¼ of the total ration.