Grafting helps high tunnel growers manage soil challenges

High tunnel production delivers many benefits, but soil-based problems such as disease, compaction, salinity and stress can limit productivity. Vegetable grafting in high tunnels offers growers a promising solution by combining the strengths of two plants — the shoot of one and the rootstock of another — to increase vigor, yield and resilience.

Grower acceptance of grafting

Tomatoes and watermelon have long benefited from grafting, and the practice is gaining ground in peppers, cantaloupe, eggplant and cucumbers. Still, grower opinion remains mixed.

“It sometimes falls in a 2:1:1 pattern,” said Matt Kleinhenz, Extension specialist in Ohio State University’s Department of Horticulture and Crop Science. “If I ask four growers about grafting, two will favor it, one will have a negative opinion — generally because of cost — and one is uncertain.”

Kleinhenz discussed the practice of vegetable grafting in high tunnels during the Great Lakes Fruit, Vegetable & Farm Market EXPO, held virtually in 2020.

Soilborne disease solutions

Soilborne diseases remain the leading reason high tunnel growers adopt grafting. Resistant rootstocks can help manage threats when available, though not all scions respond equally.

“There are many soilborne disease in high tunnels. Grafting doesn’t address all of them,” Kleinhenz said. “It has to be a disease for which a resistant rootstock is available.”

Resources such as the USDA Specialty Crop Research Initiative’s Vegetable Grafting Project offer rootstock tables developed with input from companies and maintained by Ohio State University’s Vegetable Production Systems Laboratory. Researcher continue developing rootstocks that tolerate temperature extremes, variable soil conditions and even improve fruit quality.

Economics of grafting

Economics play a critical role in whether growers adopt grafting. Higher costs must be weighed against higher yields or better quality.

“Grafting can help enhance and maintain market presence when vigor and yield are very important,” Kleinhenz said. “There are growers who are very keen on total, seasonal yield.”

Smaller growers, especially organic operations, were among the first to adopt grafting due to limited land and fewer management options. Break-even analyses, such as the University of Florida’s Vegetable Grafting Decision Support Tool, help growers determine when grafting is profitable. Sometimes a lower plant population of grafted plants can achieve the same yield as higher populations of non-grafted plants, altering the cost equation.

Management adjustments required

To achieve the full benefits of vegetable grafting in high tunnels, management practices often need to change.

“Grafting may require significant changes in fertilization, irrigation and spacing,” Kleinhenz said. “If you don’t change management practices, you may not maximize the potential of the grafted plants.”

Grafting may also complement microbe-containing biostimulants and improve reduced-till systems, offsetting common yield losses.

Balancing benefits and risks

Kleinhenz cautioned that grafting itself can spread disease in greenhouses since every plant is handled twice. Yet, with more resistant rootstocks available and more growers reporting positive results, adopting is expanding.

“There are issues and some risk, but grafted plants have the proven potential to make the most efficient use of high tunnels and generate the most value,” he said.

For growers facing soilborne disease and productivity challenges, evaluating vegetable grafting in high tunnels offers a pathway to healthier crops and stronger returns.

 

 

— Dean Peterson, VGN correspondent