A bale of hay falls off the back of Jeff Kelman's 1959 John Deere 14T baler as he pulls it along his hay fields in Glenburn in 2011. Credit: BDN file photo

Moisture and hay are sworn enemies.

Not only will wet hay grow mold that can be unhealthy for farm animals, but the microbial activity can generate so much heat that the bales will light on fire. Every farmers’ worst nightmare is to wake up to see their barn aflame due to a damp bale of hay.

Sprinkling salt over bales of hay is a tradition some farmers have used for added assurance that the moisture is drawn out of their hay. However, scientists and farmers who use this practice agree that no amount of salt can replace the value of quality, well-dried bale — especially when it comes to spontaneous combustion.

Al Tilton, a farmer who lives in Prentiss, said that he has been salting hay bales since his childhood growing up on a cattle farm in Pennsylvania. He will grab a handful of feed-grade salt and sprinkle it over his bales, which he orders locally.

“All hay is going to sweat, no matter how dry it is. It’s just the nature of the product,” Tilton said. “Putting the salt on it just helps to draw out that moisture.”

Tilton has a YouTube channel called Tilton’s Heritage Pastures where he uploads videos from his farm, including the occasional how-to. He said that his video on salting hay bales gained particular attention when he posted it a week ago.

“A lot of people would come out of the woodwork and say, ‘we used to do that as a kid,’” Tilton said. “It’s not a new practice, but maybe a forgotten practice.”

But, as Richard Kersbergen, Extension Professor, Sustainable Dairy and Forage Systems, explained, salting hay is not a foolproof tactic for drawing water out of damp bales.

“There aren’t any university research sites that advise using salt to keep hay from molding or heaving,” Kersbergen said. “In reality you would have to use so much salt, especially if the hay is baled, it would impact the ability of the animal to eat that hay. You can salt the top of the bale and think about drawing water out, but it’s really not antimicrobial.”

Hay bales. Credit: Stock image / Pixabay

The real trick is to dry out hay sufficiently before putting it in bales, Kersbergen said. Hay should be at less than 15 percent moisture before it is rolled into bales, even lower for round bales.

Tilton agreed.

“Salting is not going to save a bale that’s not dried out enough,” Tilton said. “You should always buy the highest quality hay you can get. Hay can be very dangerous if it’s baled wet or green.”

Tilton said that there is a misconception that simply salting bales of hay will prevent them from spontaneously combusting.

“That’s not what salting hay is about,” Tilton said. “It’s just to keep the moisture content low and [make] healthier feed for the animals.”

In Maine, where Kersbergen said moist conditions make hay drying difficult, some farmers have moved toward anaerobic fermentation to avoid the moisture problem altogether. The hay is stored at a higher moisture level and machine-wrapped tightly in plastic to keep oxygen out. The result is a stable, fermented product that livestock find palatable and won’t set your barn on fire.

Kersbergen said that applying agents like propionic acid while baling can also help prevent molding in hay bales.

For farmers like Tilton, who prefer to keep synthetic chemicals out of their practices entirely, a sprinkle of salt is just an added assurance, but not a replacement for a well-dried bale of hay.

“The bales are going to sweat no matter how dry,” Tilton said. “It’s just an outlet for the moisture to go to.”