Research projects aimed at improving sweet potato production are under way in Mississippi and with collaborators in other states, says Steve Meyers, northeast regional Extension specialist at Pontotoc, Miss.

Meyers, who joined Extension in January, is also serving as the state’s sweet potato specialist.

“With sweet potatoes, you’re selling a unique package of water, wrapped up in edible form,” he told growers at the Mississippi Farm Bureau Federation’s summer sweet potato commodity meeting at Thorn, Miss. “Our goal is to listen to you and to try and conduct research that will help you improve yields and quality of your product.”

This involves a multi-discipline research, he says, including specialists in production, ag and biological engineering, weed science, nematology/pathology, entomology, food science, and ag economics.

At the Producer Advisory Council meeting, held in February each year at Verona, Miss., “Sweet potato growers tell us what kind of problems they’re facing and what they’d like to see us consider for research projects,” Meyers says. “Then we go out and visit with growers on their farms and listen to what they tell us, and from all that input we develop proposals for research.

 “From there, it’s a matter of finding funding to support that research, on Mississippi State University property, at our experiment stations, and on-farm,” he says. “There are at least 12 on-farm studies this year with at least 10 growers, stretching across the sweet-potato growing region of the state. We currently also have submitted proposals for grants to support research in sustainability, and a multi-state project that has a climate change component. Grants we’ve received in the specialty crops sector have also helped fund sweet potato research.”

At this year’s Producer Advisory Council meeting, grower suggestions included the need for additional research on varieties, pest management (nematodes, weeds, and insects), and added value uses for non-marketable sweet potatoes.

“We are part of a multi-state organization, the National Sweet Potato Collaborators Group,” Meyers says. “This includes Extension and research specialists from Land Grant universities across the country, and we meet yearly to discuss research programs. One of the major components of this program is sweet potato breeding. North Carolina State University and Louisiana State University submit lines for group members to try in their states.

“We evaluate things like sprout production, yield, flesh color, storage, root shape and root shape uniformity, It’s interesting to see how some of these variables change from state to state. In 2012, varieties submitted to collaborators were grown in Alabama, Arkansas, California, Louisiana, Mississippi, New Jersey, North Carolina, Oklahoma, South Carolina, and there were even some trials in Canada.”

“Lines that are being grown in Mississippi this year include Orleans/L05-111, a variety that’s being grown more in this state; three other Louisiana advanced lines, L04-175, L06-052, L07-146; a North Carolina advanced line, NC07-364; and standards Covington and Beauregard (B14 and 63).

“Our annual sweet potato field day will be held Aug. 22 at the Pontotoc Ridge-Flatwoods Branch station, with registration tentatively set at 8 a.m. At that time, we’ll dig some of these varieties and you can see firsthand how they’re performing.”

In addition to the other trials, Meyers says, “We’re growing some advanced lines from Don LaBonte, LSU sweet potato breeder. We have one study in Webster County with 16 of his advanced lines and three standards to see how they perform in Mississippi soils. Don and I will harvest them this fall and evaluate yield, root quality, and nematode tolerance, which is a concern for a lot of growers. He has five other locations in other states.”

Mississippi research projects

Other sweet potato research projects under way in Mississippi include:

Ÿ· ŸŸŸA study by Ramon Arancibia, assistant research professor at the Pontotoc Flatwoods Experiment Station, on variety resistance to tip/end rot. The 2011-2012 study on the station showed that current commercial varieties are among the most tolerant to the diseases, Meyers says.

“In on-farm studies, he found ethephon, which some growers have expressed interest in using to help set the skin on the sweet potato root, increased the incidence of tip rot, but not end rot. He also found that fast curing (85 degrees at 85 percent humidity for five days) reduced both tip and end rot.

ŸŸ· ŸŸŸAnother study on-farm and at the station from 2010-2013 looked at the effectiveness of biofungicides to reduce the incidence of tip and end rots. Arancibia dipped sweet potato slips before planting, and also had a treatment where he sprayed the biofungicide in the furrow.

“He’s had variable results in reducing rots,” Meyers says. “We hope to get more concrete data this year. We know that rain and soil moisture at harvest also appear to be a factor in incidence of these rots, and that ethephon, regardless of the biofungicide applications, still increased tip rot incidence.

“Benny Graves, executive director of the Mississippi Sweet Potato Council, and I have two sites in Chickasaw County where we’re looking at one of the biofungicides, Serenade Soil, and a conventional fungicide, Ridomil Gold, on tip and end rots. We’re comparing 1/2-gallon per acre of Soil Serenade and 1/2-pint per acre of Ridomil Gold with non-treated plots. The applications are made in transplant water at approximately 150 gallons per acre. We’ll harvest, store, and rate them for end and tip rots.”

Ÿ· ŸŸŸŸNematodes are a significant concern for sweet potato growers, and Gary Lawrence, associate professor of biochemistry, molecular biology, entomology, and plant pathology has a study on the MSU north farm, looking at use of foliar VydateL in-furrow at planting and foliar applications for managing plant parasitic nematodes.

“VydateL is labeled for a 2 gallons per acre preplant application, but it costs $100 per gallon — an expensive treatment. He is looking at the impact of both in-furrow and foliar applications on nematode populations,” Meyers says.

“He, Mark Shankle, research professor at the Pontotoc Flatwoods Branch Experiment Station, and I are looking at a comprehensive systems approach for nematode management systems. The on-farm study in Calhoun County is comparing K-PAM, VydateL, and Mocap pre-plant and VydateL (foliar 14 and 28 days after planting) on reniform nematode populations and sweet potato injury. This covers 3.6 acres — a huge study.

“We’ll take soil samples across all plots, record nematode numbers, rate plants for vigor, and collect yields at harvest. This should give us some information on how VydateL stacks up against the other materials in Mississippi sweet potato production — basically to see if we can find more economical ways for nematode management.”

Ÿ· ŸŸŸŸWeed management: “Sweet potato growers contend with a lot of different weeds,” Meyers says, “but yellow nutsedge is one of the major problems. We don’t have a lot of options to control it right now — Dual Magnum is about the only material that’s labeled, but it requires rainfall for activation, and that’s something we don’t always get when it’s needed.

“Mark Shankle and I are conducting a study to determine yield and quality loss caused by yellow nutsedge interference at various densities. We have on-farm locations in Chickasaw County and Nash County, N.C. Hopefully, this will tell us how much yield we’re losing to nutsedge and will help aid management decisions.

“We’re also evaluating nutsedge management systems, looking at the effect of different mechanical and herbicide options for control, at one on-farm location in Chickasaw County and one on the research station. We divided fields in half. Half was cultivated, the other half was do-alled and sprayed with burndown and postemergence herbicides or a tank-mix of preemergence herbicides.

“We’re also continuing to evaluate Fierce, a new Valent herbicide, to see if it will fit in a weed management program and to determine crop safety when heavy rainfall occurs after application.”

Advanced scanning technology

ŸŸ· ŸŸŸMark Shankle and Kambham Reddy, MSU research professor of plant and soil sciences, have a project to look at at the influence of Dual Magnum on root development. “They are using an advanced scanning technology winRHIZO image analysis system to look at architecture of roots,” Meyers says. “They should be wrapping up this study pretty soon.”

Ÿ· ŸŸŸŸRamone Arancibia is also looking at storage root initiation. “We’ve had a multi-state grant over several years to develop practices to improve storage root initiation,” Meyers says. “We know that high temperature reduces storage root initiation, and he’s evaluating the use of growth regulators to alleviate some of that stress and set more roots.

“He’s also looking at some sustainable production systems to determine the beneficial effect of winter cover crops and the feasibility of no-till production. He has two on-farm studies and one on the Pontotoc research station. He’s been working on this for several years and has found that winter cover crops improve soil characteristics and that sweet potato yields after cover crops were similar to conventional production.”

Ÿ· ŸŸŸŸJohn Ward, Mark Shankle, and Ramon Arancibia are working on development and testing of a sweet potato undercutter, for an alternative method of increasing sweet potato skin strength prior to harvest. The work is being done at the Pontotoc station and on-farm.

“Essentially, what they’ve found is that undercutting about six days before digging tends to increase skin toughness over mechanical de-vining in the Beauregard variety,” Meyers says. “In the future, bulk harvesting or modified harvesters could be an option. This research insures that growers have options in the tools they use for setting skin pre-harvest to maximize post-harvest performance.

ŸŸ· ŸŸŸNew post-harvest tools: Meyers is working with John Ward and John W. Lowe, agricultural and bioengineering research associate at MSU, to determine the effect of post-harvest conditions (curing method, relative humidity, temperature, air movement) on weight loss (transpiration) and quality of sweet potato storage roots over time.

“We have two platform scales our ag engineers have built with four load cells each. We can stack six 20-bushel bins on the scale to see how storage and curing conditions affect weight loss of sweet potatoes over time. Each unit has a datalogger to measure relative humidity and air temperature every hour, with a digital readout to easily view weight change.”

Ÿ· ŸŸŸŸResearch that is pending funding includes a block grant proposal for Meyers and Shankle to investigate pre-plant soil fumigants for sweet potato pest management. The objective is to compare K-Pam fumigation treatments with the next best options for disease, insect, and weed management systems. The proposal includes two years of research, with an on-farm component each year.

Ÿ· ŸŸŸThere is, Meyers says, a SARE (Sustainable Agriculture Research and Education) proposal to develop a sweet potato-cattle production system for Mississippi. “It would determine the best means to incorporate sweet potatoes into cattle diets, including minimal processing efforts. We’ve submitted a pre-proposal, with full proposals invited in August, and recipients to be announced in November.” Research would be by Meyers, John Ward, Stephanie Ward, and Arancibia.

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At the Pontotoc station, Meyers says, a foundation seed production program is maintained “to insure that there are virus-tested G0, certified true-to-type plant materials for growers in Mississippi, and to provide the state’s sweet potato industry with certified propagation material that is disease-free and true to type. Certified propagation material is produced every year, according to demand, and new varieties are incorporated into the program, also according to demand.”