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Silo Gas Poisoning More Likely During Drought

Excess nitrates in silage crops lead to increased development of silo gas (nitrogen dioxide) from the crop when it is put into the silo. Plants wilted by the drought, or crops ensiled just after a prolonged drought followed by a rain are likely to have excess accumulation of nitrates in the plant material.

Two recommendations to help limit excess nitrates when making silage are to 1. avoid harvesting crops immediately after a rainfall, and 2. cut the plant a little higher than normal. Much of the excess nitrates are stored in the lower portion of the stalk.

Reduce the Danger during and after Filling


1. Nitrogen dioxide gas can form within hours of filling the silo and may last for a period of two or three weeks. Farmers are advised to stay clear of the silo for a period of three weeks after filling. After this period of time, the danger of nitrogen dioxide gas is greatly reduced; however, steps should be taken to adequately ventilate the silo before entering. Running the forage blower for fifteen to twenty minutes with the door closest to the level of silage open, is recommended.

2. Be on the alert for bleach-like odors and/or yellowish brown fumes at the base of the silo.

3. The silo chute door closest to the level of silage should be open. This will allow the nitrogen dioxide to escape when the blower is turned on. Adequate ventilation at the base of the silo, for example, in a feed room, should be provided to expel the gas. Silo feed rooms should be ventilated by the use of open windows and fans, for a period of three weeks after filling the silo.

4. Keep door(s) between the silo or feed room tightly sealed to avoid contamination of barn areas.

5. Silage distributors should be adequate for the silo and properly adjusted to ensure uniform distribution of silage; this will make it unnecessary for an individual to be continually, manually, leveling silage during or after filling.

If entry into a silo is absolutely necessary within the first 10 days after filling, a self contained breathing apparatus should be worn. Additionally, an observer should be stationed on the silo blower platform and visible contact with the person entering the silo maintained.

For more information on silo gas poisoning refer to "Silo Gases - The Hidden Danger," Agricultural Engineering Fact Sheet Safety 16, available from your county extension office or Penn State's Agricultural Engineering Department.

Source: Dept. of Ag. Engineering