And the work by Texas A&M University associate professor Daniel Leskovar and his group at the Texas A&M Research and Extension in Uvalde has caught the attention of Cliff Chambers, production manager for Duda of Texas in McAllen, Texas.

Chambers, who has been following Leskovar’s trials, says the system holds promise if onion prices would remain consistently higher than the $4 to $5 per 50-pound bag they’ve been averaging the past two years. “I think those years where you have a good market, particularly about two years ago when it was a $10 to $12 market, that is when you’re going to take it to the bank with drip and transplants,” Chambers says. “I think (the system) has great potential, but it’s hard to sell to growers when you aren’t making any money direct seeding and furrow irrigating...”

One area that may lend itself to the transplant and drip irrigation system is the production of specialty onions, particularly those sold in cartons, Chambers says. Onions that would typically net $6 to $7 for a 50-pound bag could bring as much as $10 to $12 if sold in cartons. But to garner the higher prices, the onions have to be big and uniformly shaped, he says. “If you could guarantee that kind of quality onion with drip and transplants, you could pretty much do it,” Chambers says.

In his trials, Leskovar examined three onion varieties: Legend, the new improved 1015 from Texas A&M vegetable breeder Leonard Pike’s breeding program; 1015; and Texas Early White. He compared direct seeding of the three varieties to 9- to 12-week-old greenhouse-grown nursery transplants. Part of the experiment also examined irrigation practices to see if growers could reduce the amount of water they applied and save on irrigation costs.

Growers in the Wintergarden vegetable area, centered around Uvalde, draw irrigation water from the Edwards Aquifer. The same underground reservoir also serves Austin and San Antonio, both of which are growing and placing increasing demands on the already over-drafted aquifer.

Chambers oversees operations in the Rio Grande Valley, which is served by Falcon and Amistad reservoirs. Both are critically low because of prolonged drought, and some south Texas irrigation districts are already warning of curtailed water deliveries next year. The drought, as well as the increased flexibility drip irrigation provides, has prompted Duda to switch more of its onion acreage to the low-flow system. This year, about 80 percent of the company’s 500 Rio Grande Valley onion acres are on buried drip. Drip is not cheap, however, costing about $400 per acre.

As part of the experiment, Leskovar wanted to determine the optimum depth for buried drip, comparing 2-inch-deep tubing to 6-inch-deep placement. He also wanted to see what, if any, effect reducing irrigation from 100 percent ET (evapotranspiration rate) to 50 percent after plant establishment would have.

Area growers typically direct seed four lines per 40-inch bed, a practice Leskovar applied to the trials. He planted the transplants on two lines per bed with 4.25-inch spacings between plants.

Nevertheless, he found the transplant survival was much greater than the direct-seeded plants, and plant stands were comparable in the end.

Weather during the two years of trials was just the opposite, putting the transplant system to the test. Conditions during 1999-2000 were nearly ideal, with the transplants being planted Dec. 1, 1999. Leskovar and his crew direct seeded the onions on Nov. 15, 1999.

During the 2000-01 season, rain kept them from transplanting until Jan. 9, 2001. That meant the greenhouse had to hold the transplants for three additional weeks. Although the delay would cost a grower additional nursery-related charges, it proved to Leskovar that the transplants remained viable and still performed well in the field. The trials were direct seeded on Dec. 20, 2000.

We knew the season was going to be reduced because of the late planting,” Leskovar says. “Still, under the conditions, which were less than favorable compared to the year before, we still showed a positive return for the transplants.”

During each year, they graded the onions after harvest into super colossal, colossal, jumbo and medium. “The first question was how well did the transplants do in terms of yield and quality,” Leskovar says. “We determined that the yields were increased and there were a higher number of larger-sized onions, which leads to more money for the growers.”

Based on the economic analysis, growers would have made more money using the transplants because of the larger number of larger-sized onions. In fact, during the challenging 2000-01 season, growers using transplants would have made $430 per acre compared to losing $680 per acre with direct seeding. The analysis is based on $8 per 50-pound bag of jumbos and $5 per bag of mediums. Of the three varieties, Legend appears to be the most responsive to transplanting.

Leskovar says the transplanted onions also appear easier to harvest because of a more uniform stand. They also pull easily from the ground at harvest.

In the transplanted plots, he saw less weed pressure because they could apply herbicides that require a specific plant size earlier over the top of the transplants.

A side benefit of using transplants is improved flavor. Chemical analysis of the harvested onions showed increased soluble solids and reduced pungency in the transplants compared to direct-seeded onions.

Of the four irrigation treatments, only the 2-inch-deep buried drip applying 50 percent ET reduced onion yields significantly.

More may be better
Currently, Leskovar is conducting trials into the potential of increasing seedling density within the transplant tray cells from one up to six plants per cell. He’s looking at different transplant spacings for the multiple-plant plugs. Leskovar also wants to see whether putting two plants per cell every 9 inches or three plants per cell at higher spacings will reduce greenhouse growing costs and transplant labor without affecting yields, bulb shape and overall quality.