CALIFORNIA
Vegetables A SPECIAL GROWERS’ REPORT OF AG ALERT ®
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Watermelons are harvested this month in San Joaquin County, where researchers and farmers are testing root grafting as a potential “wave of the future” for healthy plants and high-quality melons.
Field trial tests new means for growing watermelons By Vicky Boyd
different ET rates and irrigation demands. Although grafted watermelons are new to California, the technique has long been used in Europe and Asia as a way to address soil-borne pests and a lack of soil fumigants and in fields for rotation. About 15% to 20% of California’s 10,000 watermelon acres in 2021 involved grafted plants, Wang estimates. Nationwide, grafted plants probably account for about 7,500 of the 100,000 total watermelon acres, said Mark Lauman, West Coast sales coordinator for Tri-Hishtil. Through a partnership with Israeli and Italian companies, North Carolina-based Tri- Hishtil produces greenhouse-grown grafted watermelon and tomato transplants. “They each have more than 20 years experience in grafting,” Lauman said of the partner companies. Wang’s current trial involves five hybrid squash rootstocks, one citron melon rootstock and one bottle gourd rootstock. All belong to the same cucurbit plant family as watermelons. He selected them based on past performance in trials and disease tolerance. The rootstocks are grafted with Warrior seedless watermelon scions, which produce oval, dark-green-striped, red-fleshed fruit weighing about 16 to 18 pounds each. Matching the proper scion to the rootstock can be an art because not all pairings
Grafting, which involves marrying a scion variety to a related hardy rootstock, has been touted as a way to build a better plant. Now the theory is being put to the test in a watermelon field in San Joaquin County. Near Ripon, a study by Zheng Wang, a University of California Cooperative Extension vegetable crops and irrigation advisor for Stanislaus, Merced and San Joaquin counties, is comparing the performance and economics of grafted watermelon plants to ones on their own roots. The trial is being closely watched by Van Groningen & Sons, a Manteca-area melon and pumpkin producer that has planted grafted watermelons on part of its acreage for the past three years. “We’re learning about it,” said David Jarrett, the farming operation’s planting manag- er. “You’re potentially looking at the wave of the future. It’s an expensive new growing technique, but we’re seeing an advantage doing this. We have fewer plants per acre, yet we’re still spending more per acre. But you’re going to have healthier plants and you’re going to be bumping the yields up a little bit.” In complementary research, Wang is validating crop-specific evapotranspi- ration rates—or irrigation water the plant transpires combined with what evap- orates—for grafted watermelons. Because of their potentially different growth patterns compared to nongrafted plants, Wang said, grafted plants may have
See GRAFTING, Page 12
July 20, 2022 Ag Alert 11
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