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Sweet Potato Storage Pit Results

April 14, 2009

At the end of November we buried sweet potatoes between thick layers of hay in an underground storage pit. For four months we recorded air and storage pit temperatures hourly using thermocouples attached to a datalogger. The pit temperatures stayed in the ideal range — between 13 and 16 °C (55-60 °F) — through December. They fell a little below optimum in January, returned to the ideal range in February, and got a little warmer than ideal in March. Air temperature routinely dipped below freezing during the storage period, but pit temperature stayed well above freezing.

Daily average temperature in a sweet potato storage pit (orange) and surrounding air (blue), December 2008 through March 2009. Blue bars show daily air temperature range. Yellow area shows ideal range for sweet potato storage.

Daily average temperature in a sweet potato storage pit (orange) and surrounding air (blue), December 2008 through March 2009. Blue bars show daily air temperature range. Yellow area shows ideal range for sweet potato storage.


We collected sweet potatoes from the pit in mid-February to serve at a field day and an event showcasing the work of local chefs. The sweet potatoes were delicious.

Sweet potatoes collected from the storage pit in mid-February. About 80% of potatoes collected were still marketable. Culls are shown to the right of the bushel basket.

Sweet potatoes collected from the storage pit in mid-February. About 80% of potatoes collected were still marketable. Culls are shown to the right of the bushel basket.

We collected the rest of the sweet potatoes in late March, to start slips for this year’s crop. By the final collection most of the sweet potatoes were rotting, leaving about 25% for slips. Rot appeared to be associated with excessive moisture in the pit. The tarp that covered the pit was not enough to keep it dry during the spring rains.

The thermal mass of the soil kept storage temperatures near optimal for sweet potatoes, but digging the sweet potatoes up whenever we wanted to serve them was a lot of work. Our experience convinced us that we need a proper root cellar on the land, to keep moisture out and make collection easier.

Michael Bomford provides research and extension services related to organic agriculture and small-scale renewable energy production through Kentucky State University’s Land Grant Program. He thanks Harold Benson, John Clay, Brian Geier, Eddie Reed, John Rodgers, Hank Schweikart, Steve Skelton, and participants in the 2008 Limited Resource and Minority Farmers’ Conference at KSU for guidance and help with construction of the sweet potato storage pit. Brian Geier collected the sweet potatoes after storage.

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