Answer: Two very different causes can produce the symptoms you describe, says Jonathan Schultheis, sweetpotato specialist at North Carolina State University in Raleigh. If the cracking is irregularly spaced all around the roots, then the problem was extreme moisture fluctuation at harvesttime. If the cracking was mostly around the tips of the roots, cut one open and look for black, pin-sized dots, which indicate nematodes. Both are common in North Carolina and, if severe, the damage can greatly deform the roots, he explains. Certain varieties, such as Jewel, are very susceptible to cracking and deforming when dry conditions are followed by wet weather at harvesttime, says Schultheis. The best solution is to grow a crack-resistant variety like Beauregard. Keep the plants evenly watered and mulched with straw or hay to prevent moisture fluctuations and subsequent cracking. If you suspect nematodes, have your soil tested at a state university laboratory, Schultheis recommends. Rotate crops, planting soybeans or winter wheat in the sweetpotato area for one or two years to lower the nematode population. You can also plant nematode-tolerant varieties, such as Jewel, which will reduce, but not eliminate, the damage. Solarizing the soil with 4-mil-thick clear plastic for six weeks during the summer will heat it up enough to kill many of the nematodes, he adds.
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