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Sweet Potatoes on the Rise

Moving toward mechanization and processing
By Nancy Riggs




Sweet potatoes are harvested with a Standen harvester at Thornhill Farms.
Photo courtesy of LSU Sweet Potato Research Station.

While sweet potatoes make up only a small portion of the state's economy, the industry is important. There are about 7,500 acres currently in sweet potato production, and in 2010, ConAgra Foods opened a $156 million processing and packaging facility in Delhi, La.

Louisiana State University (LSU) hosts the only university research station devoted exclusively to sweet potato production and research. The LSU Sweet Potato Research Station is one of 10 sites of the LSU Agricultural Center, known as LSU AgCenter, based in Baton Rouge, La., with both research and extension sectors.

The increased interest in sweet potatoes is driving a shift in production from fresh market to processing, with more than half of Louisiana's sweet potatoes now going to processing. A decade ago, about one-third of the state's sweet potatoes went to processing - mostly canning.

Technology is leading the way toward mechanized harvesting, with field trials under way in northeast Louisiana. Concurrently, LSU research is developing new varieties that will work well for processing and mechanized harvesting. While sweet potatoes are a high-profit crop, the amount of labor required contributes heavily to production costs.



The Evangeline sweet potato was developed at the LSU Sweet Potato Research Station.
Photo courtesy of Dr. Don LaBonte, LSU.

Growing sweet potatoes

Ken Thornhill, 71, has grown sweet potatoes at Thornhill Farms, Wisner, La., for 42 years. He's president of the Louisiana Sweet Potato Commission and the U.S. Sweet Potato Council. He was a chemist before returning to the family farm following his father's early death in an auto accident.

"I have a major sweet potato research facility just 8 miles away," Thornhill noted. "I used to grow a lot more, but I've cut back to about 250 acres." Increases in the processing segment of the sweet potato market have led to changes in Thornhill's production. He used to grow primarily for the fresh market, but now he contracts 100 percent of his crop to the ConAgra plant for sweet potato fries. Knowing that his crop is sold before it's produced means there's one less thing for him to worry about.

Even though he's cut back on acreage, Thornhill hasn't cut back on his interest in technology to increase efficiency and profit. He's incorporated technology into growing sweet potatoes and is a leader in moving sweet potato production toward mechanization.

Several years ago, Thornhill began working on a mechanical harvester. After he developed a prototype of the harvester, he contacted Kevin Pinelli, owner of Farmer's Harvest, Inc., Dover, Del.

"I've been in the equipment business for white potato production and handling equipment for 17 years, and I saw an opportunity in the sweet potato industry," Pinelli said. Farmer's Harvest distributes Standen equipment (http://www.standen.co.uk/products), which is manufactured in the U.K.

Pinelli was so impressed with Thornhill's prototype that he encouraged Standen representatives from the U.K. to visit Thornhill Farms. After viewing the prototype in operation at the farm, Standen representatives moved forward with engineering a sweet potato harvester for both the fresh market and processing industries.



Ken Thornhill, center, discusses the mechanical harvester being used at Thornhill Farms.
Photo courtesy of LSU Sweet Potato Research Station.

A cleaning table removes field trash during the harvesting process, and a sizer sorts the sweet potatoes by size. When used to harvest sweet potatoes that will be processed, the sizer can be closed off, since size isn't a factor for processing.

A Standen harvester, based on Thornhill's prototype, is in operation at Thornhill Farms, and two harvesters are in use at North Carolina sweet potato farms. Pinelli noted that vines must be removed prior to mechanical harvesting, and both vine pullers and vine choppers are being evaluated.

LSU Sweet Potato Research Station

"Our biggest problem with having growers is attrition of older growers," said Dr. Tara Smith, research coordinator at the LSU Sweet Potato Research Station. "Our growers have struggled in the past few years, following two consecutive years that brought major hurricanes to the coast and flooding farther north. Labor costs have continued to increase production costs."

LSU began its foundation seed program in 1934, followed in 1949 by the establishment of the research station on 300 acres in Chase, La. About 15 years ago, the foundation seed program was upgraded to a virus-tested foundation seed program. The research station annually produces between 10,000 and 15,000 bushels of foundation seed, which is sold to Louisiana producers for seed production operations and to out-of-state producers once in-state needs are met.

Variety development research is conducted at the research site, with variety trials in a number of states. Two of the popular commercially grown varieties, Beauregard and Evangeline, were developed and released by the research station.



Sweet potatoes are harvested from variety trial plots at the LSU Sweet Potato Research Station.
Photo courtesy of Dr. Don LaBonte, LSU.

Industry shifts drive research

Dr. Don LaBonte, LSU professor and sweet potato breeder, said, "Although our acreage is down now to about 7,500 acres, we are a major processing state." He cited the importance of the ConAgra french fry plant to the sweet potato industry. "We now have traditional potato growers from Northern potato regions growing sweet potatoes in the South. They have brought with them production strategies used in the white potato industry and adapted them to sweet potatoes," he said.

The major traits sought are high yield and disease resistance, but growers also face rising production costs and crop losses due to flooding.

"The fresh market is conservative with what a sweet potato should look like, but interested in and slowly moving into offering several varieties with varied skin color and flesh color, both white and orange. Progressive growers already see this coming, and upscale grocers are already doing this. We try to fit new market niches and provide varieties with different flavors. We want stores to offer more than one variety, and we are starting to see this," LaBonte noted. He cited a new release, 04-175, with bright red skin, deep orange flesh and high sugar content.

The processing industry includes a number of products, from chips to fries to juices. LaBonte said, "The processing sector is building fast and may push us to develop processing varieties with unique attributes, such as high dry matter and deep orange flesh."

An exclusive variety release, 07-146, was made to ConAgra. LaBonte describes it as "a unique variety that has very nice properties for french frying. It has a double-digit yield advantage over other varieties, so it is gaining production acreage."



The Murasaki sweet potato has a red skin.
Photo courtesy of John Wozniak, Louisiana Cooperative Extension Service.

LaBonte said, "Fresh markets like the silky skins, which are susceptible to skinning injury. We are in need of more durable skin to aid in developing varieties suitable for bulk harvest and storage."

Looking ahead

LSU variety development field trials are located in a number of states in different soil types to evaluate unique fits for specific areas. Research and field trials continue to help growers meet the challenges of increasing yields without increasing costs, and to develop varieties that will best meet market demands.

Technology continues to play a major role in the sweet potato industry. Thornhill cited a ConAgra grant to Louisiana Tech University in connection with the development of a mechanical sweet potato slip planter. Smith noted that with increased labor regulations and costs, mechanization is important to the sweet potato industry. She said, "Labor is a major contributor to production costs. Mechanical harvesting will offer a real benefit to our growers."

Nancy Riggs is a freelance writer and frequent contributor. She resides in Mount Zion, Ill.