Johnson sums up 12 years of researching vegetable crops
HARRINGTON, Del. — With retirement approaching this summer, Dr. Gordon Johnson, Extension fruit and vegetable specialist at the University of Delaware, reviewed more than a decade of his team’s applied research on processing vegetables during the vegetable sessions of Delaware Ag Week on Jan. 11
He started with the introductory slide from a talk he had given at the Pickle Packers International meeting, where he won the gold pickle, the highest award the organization gives.
The research focused on fertility and production of gynoecious and parthenocarpic pickle varieties.
Gynoecious varieties produce only female flowers and have a more concentrated period of fruit production and parthenocarpic varieties are seedless and sets fruit without pollination.
Light skin color in cucumbers was a problem for pickle growers in the East, as was length and diameter.
“We did nitrogen trials,” Johnson said. “We found higher nitrogen increased the color, but we’d never use that much nitrogen. … “We added sulfur, and that made the pickles greener.
“But as a side effect, it also made the pickles longer, so they wouldn’t fit in pickle packers’ jars. They’d have to cut off the ends.”
He also studied the effects of magnesium and sulfur and continued variety trials of gynoecious varieties.
Researchers looked at nitrogen rates and found there were issues with too much vine growth. Certain varieties peaked at 80 pounds of nitrogen.
Downy mildew resistant pickles still had issues with mildew. They needed fungicide treatment to get full yields. It is possible to make fewer applications if timed just right, Johnson discovered. Trials found mildew-resistant varieties did produce higher yields.
Johnson also studied parthenocarpic pickles — varieties that do not need to be pollinated to produce fruit — starting in 2010 through 2022. There are several breeding programs, Johnson said and some varieties are gaining acceptance in the industry.
In fields planted at half the normal population, Johnson saw higher potential yield, good size distribution, and often better color. There were some issues early on, more variable than desired.
“We found some promising varieties. Bowie and Gershwin are becoming the industry standard,” Johnson said. “Then we brought in European types with thinner skin that are less chewy. Did you know there’s a person in the factory whose job it is to make sure pickles are not too chewy?”
Looking at plant populations, researchers planted trials in small plots in May/June and July for nine years. Earlier trials had top yields of 469 bushels per acre. In later-planted crops, yields dropped down. “Heat affects yields,” Johnson said.
Researchers looked at the adaptability of varieties in different environments.
“Yield stability is an issue. Some varieties are more stable than others. We will look at that, planting in monthly intervals,” he said.
Peak temperatures reached the high 90s to 100 degrees, which is hard on pickles. “We found a number of good varieties,” he said. “Amarok had good yield across the season; Bowie had high yield potential but was less stable.”
Johnson and fellow researcher Dr. Emmalea Ernest, with the help of graduate students, also studied lima beans, studying no-till, inoculation, seed production, populations, specialty types, root knot nematode and phytophthora capsica and other factors.
They also studied heat stress mitigation. “Is there anything we can do for heat loss in limas?” he asked. They tried growth regulators, no-till, different varieties, inoculation and particle film. “None work as well as Emily’s work in breeding,” Johnson declared.
Sweet corn trials included no till, nitrogen rates, cover crop use, planting density and other variables.
Johnson also conducted variety trials in greens, pickles, processing peppers, beets, broccoli, specialty brassicas and Brussels sprouts.
He tried various methods of crop management — irrigation rates, populations, planting dates, overwintering, cutting management and no-till in lima, pea, corn and snap beans.
With specialty limas, he tested freezing and dry seed production, which is not something that can be done consistently here, he said.
Large grant funding will be needed to continue work on processing limas.
Johnson has worked extensively on broccoli. Noting that a lot of broccoli comes from Central America, he said, “We hope to be able to grow it here for our processors.”
He tried direct seeding in July, as many as 21 varieties. His team evaluated cut florets, examining recovery, cores and how they froze, counting how many large florets were produced when cut.
“Companies would like a range of florets,” he explained, “because different customers require different sizes. We provide that information in these trials.”
The core is a problem. “We’re trying to eliminate a big core,” he added.
Blonding, or yellow coloration, is also a problem in broccoli. Consumers want full green color.
“We are continuing frozen sample evaluations. One company brought its product development team in and were surprised at what we did here,” he said.
“Imperial is a good variety for us, but a lot of blonding makes it less desirable.” Spectre is a new variety with less blonding, like the industry standard, Emerald Crown.
Johnson also worked with specialty cole crops such as broccolini, sprouting broccoli, and caulilini. Sprouting varieties make good spears, he noted. With one cut, you get all the spears. They are a cross between regular and Chinese types, which are more delicate and require individually freezing on a tray. Johnson grew purple sprouting broccoli, but discovered when blanched, it turns green. “So why bother growing it for processing?” he questioned.
Caulilini, or sprouting cauliflower, has a green stem, not white. The florets are on spears. “We are excited to see this as a new product,” Johnson said.
Another new project is looking at Brussels sprouts, which are being evaluated now. Plants were still in the field during Ag Week. Researchers are looking at whether there is disease or not. The variety Capitola looked good, but Confidant, Dagan and Dimitri do best, he said. However, Confidant had a lot of culls.
In frozen evaluations of Brussels sprouts, Gustus had more yellow color, while Dagan came out of the freezer with dark green color. “We hope to show the industry this spring what works,” Johnson said.
He is retiring in June after 12 years as an Extension vegetable specialist, and several years before that as Kent County Extension ag agent, but said Dr. Emmalea Ernest will continue the research.
Ernest commented, “We all feel overwhelmed seeing what went on the last 12 years.”