WILSON, N.C — More than 100 operations across North Carolina now use negative horizontal ventilation to increase profits and shelf life of sweet potatoes for customers.

It's a method of forced air cooling, invented by N.C. State Professor Dr. Mike Boyette.


What You Need To Know

  • Negative horizontal ventilation allows farmers to control the humidity and temperature of storage buildings that house sweet potatoes

  • Dr. Mike Boyette with N.C. State created the storage technique

  • Before, sweet potatoes would spoil within a few months, but now farmers can keep sweet potatoes up to a year before packing them for customers

  • More than 100 operations across North Carolina have facilities with negative horizontal ventilation



“You can grow sweet potatoes from Ontario, to all the way down to Uruguay and all over the world," Boyette said. "But only the places that have invested in the infrastructure we got here...that can keep them, I mean, I have seen potatoes like this, out of the ground for 13 months.” 

The storage technique uses fans that allow farms to control the temperature and humidity in the buildings where sweet potatoes are stored. ​

“What you can guarantee is that every potato in the room, 20 feet deep, 150 feet long, 60 feet long. We are talking millions of pounds of sweet potatoes, every potato in the room is going to be at about the same temperature," Boyette said.

It matters for operations like Lancaster Farms in Wilson, because it's an export packer. Meaning, 100% of its sweet potatoes ship overseas.

"Once they leave our facility, they are on a container for two weeks," said Sarah Carraway, the farm's office manager. "There's probably three weeks between the time it gets packed at our facility, to actually hits the warehouse in the EU, UK or wherever we are sending."

Lancaster Farms Office Manager Sarah Carraway overseeing the packing line.

Carraway's family owns the farm. She says this invention, plus the potato curing process, is a game changer.

"It's a good product, it's sweeter. It's holding the sugars in it. And I also think you should invest in a curing facility like this because you're able to hold your potato," Carraway said. "So if the market was low or whatever was going on, you're able to keep your potato in a good environment until you're able to put it on a packing line."

A row of sweet potatoes planted in Lancaster Farms fields.


According to N.C. State, historically, sweet potato farmers were limited to an August through November harvest. And due to poor storage, the crops needed to sell a few months later.

Studies showed rot and poor handling accounted for the loss of half of the nation's harvest. Boyette was able to counteract that with his invention of negative horizontal ventilation. ​

According to the North Carolina SweetPotato Commission, North Carolina has ranked as the No. 1 sweet potato producing state in the United States since 1971.​