Unlike many other Mid-South crops, Louisiana’s sweet potatoes were planted at the ideal time this year. And just like other Mid-South crops, major rainfall has delayed harvest.

“We started planting in late May,” says Tara Smith, LSU AgCenter sweet potato specialist and research coordinator at the LSU AgCenter’s Sweet Potato Research Station in Chase, La. “Plantings continued into June. That’s the proper planting period and the majority of sweet potato plantings take place in that window.”

Towards the end of June, “we got into some dry conditions. But most of the south Louisiana crop had been planted and producers in north Louisiana were able to stay on track because of irrigation capabilities. For the most part, we had adequate soil moisture and very good stands were established across the state.”

South Louisiana was particularly dry during the months of June and July. Growers there were without significant rainfall for several weeks.

Sweet potato harvest usually begins in August, but dry conditions during the growing season resulted in an undersized crop. That meant producers delayed harvest until the crop “sized up a little. Initial reports indicated the crop would have good quality and average yields.”

Then, in mid-September, rain began to fall.

“Morehouse Parish in north Louisiana received the brunt of the rainfall with some producers getting in excess of 15 inches in only a few days.”

With sweet potatoes, “the concern isn’t necessarily the amount of rain but how long the ground remains saturated. The initial rain event did cause excessive concern, but as the rain continues to fall and drying time is limited, producers will become increasingly concerned.”

During the last week of September, sweet potato harvest kicked off in earnest across north Louisiana. Then, more rain arrived and shut down harvest operations again.

“Now, we’re in a holding pattern just waiting until we can get back in the field and assess the situation. We have received 7.5 inches of rainfall at the LSU AgCenter Sweet Potato Research Station since Sept. 15. But north of here, producers have received anywhere from 10 to 20 inches. Seven inches is a significant rain event, but it seems like a drop compared to 20 inches.”

Smith remains cautiously optimistic. “Right now, we’re okay but the quality of the crop will decrease if the current weather conditions persist. We know that we will have some crop loss and we need some dry conditions so we can resume harvest. This is the second week of October and we’re about 35 to 40 percent harvested across the state. We should be 70 percent complete at this time.”

Once sweet potatoes are ready for harvest how rapidly does degradation occur?

“It’s important to get them out in a timely manner for several reasons. Most of the producers across the Southeast — Louisiana, Arkansas, Mississippi and Alabama — are growing the Beauregard and Evangeline varieties. The Covington variety is also being grown, but to a lesser extent. Both Beauregard and Evangeline are 100- to 120-day varieties. Of course, several variables like fertilization and environmental factors dictate when the crop will be harvested. However, in average, 100 to 120 days is usually when the crop is the ideal size for harvest.”

Under saturated conditions, “degradation of sweet potatoes can happen quickly. Obviously, the part of the crop that’s utilized is underground and under saturated conditions the amount of oxygen available to the crop is limited. Sweet potatoes are living, breathing organisms and when oxygen is unavailable to the plant they’ll begin to break down and sour.”

When harvesting sweet potatoes in wet conditions, “you have to handle roots in a different manner. Storage conditions need to be ideal to maintain the integrity of the crop. Well-ventilated, climate controlled facilities should be used. Roots harvested in extremely wet situations should be exposed to a lot of air and should not be subjected to the normal curing process where the temperature is increased just after harvest.”

Harvesting in wet conditions can damage fields and is certainly less efficient. But conventional tillage is used in sweet potato production, so damage to the field “isn’t as big an issue as in row crops.”

Due to the extended harvest, “in areas where the crop’s integrity hasn’t been compromised, it’s possible we won’t realize our maximum amount of U.S. No. 1 (premium grade sweet potatoes).”

That doesn’t mean the roots won’t have a home, Smith is quick to point out. There are alternative markets for larger potatoes — mainly in the processing sector.

Larger sweet potatoes might become fries. A new sweet potato fry processing facility in north Louisiana is scheduled to be running next fall.

“Theoretically the potatoes that don’t meet fresh market grade could go to a facility like that. Producers are very excited about the value-added opportunities currently available and those coming into the state. This will be a great benefit to Louisiana producers — but also producers across the Southeast.”

Before harvest was halted, Smith was hearing total yields of 350 to 500 bushels per acre. The average yield for Louisiana is normally around 400 bushels per acre. About 60 percent of the yield has been premium grade.

What about Louisiana’s 2009 sweet potato acreage?

“We have about the same acreage as in 2008. We were very pleased with that because with the negative impact of the hurricanes, we thought additional acres might be lost. But thankfully most of our producers were able to come back and there are about 15,000 acres planted this year.”

A mandatory trapping and spraying program for sweet potato weevils — operated by the Louisiana Department of Agriculture and Forestry — continues in the state. All sweet potato fields are monitored for presence of the insect using pheromone traps and all fields in south Louisiana are treated with a recommended insecticide on a seven-day to 10-day schedule.

“The program has helped to maintain the integrity of the south Louisiana industry where the weevil has been considered a minor issue in recent years. The program also helps in managing other problematic insects and has allowed the majority of our production to maintain green-tag status (such a status means producers are not restricted in where they can move their crops).”

Smith says producers have found that the Evangeline variety — released in 2007 and planted on about 1,500 acres this year — has done well this growing season. “2008 was the first time we were going to get a limited commercial-scale look at the variety and then the hurricanes ruined any opportunity of doing so.

“But one thing we noticed last year is Evangeline seemed to tolerate saturated soil conditions better. We’re seeing the same thing in 2009.”

And in areas where Evangeline has been harvested, yield and quality have been “very good. Producers seem pleased with what they’re seeing and there have been a lot of inquiries about seed availability in 2010.”

The LSU AgCenter is also working with Mississippi, Texas and Arkansas producers under material transfer agreements. So far, says Smith “it appears producers outside Louisiana are also pleased with Evangeline.”

For more on Smith’s work, see http://deltafarmpress.com/news/sweet-potatoes-1105/index.html.

e-mail: dbennett@farmpress.com