Texas A&M AgriLife high tunnel study expands


By Kay Ledbetter

New opportunities such as seed production are leading to new research in the Texas A&M AgriLife Research high tunnel project near Bushland.

Dr. Charlie Rush, AgriLife Research plant pathologist and leader of the project, said the High Plains and Southern Plains continues to experience reductions in irrigation water from the Ogallala Aquifer as water levels decline, and producers need some way to improve their revenue from their farming systems.

“Our goal is not to replace the current cropping systems,” Rush said. “But not everybody has enough water to fully irrigate a corn crop or other high water-use crops. So, if they could come in and devote a couple of acres to some high tunnel production or open–field vegetable production, there is some potential to get a pretty good return and be able to take better advantage of the water they do have.

“We also know with the increased interest by consumers in locally grown vegetables, there is a growing market for that type of production in this region.”

Many researchers involved in the high tunnel projects have concentrated on water use in vegetables in the collaborative effort between Texas A&M AgriLife and the U.S. Department of Agriculture-Agricultural Research Service through the Ogallala Aquifer federal program.

Rush said getting the high tunnels established has been a struggle, with winds, water, pests and disease issues, but he feels they are getting many of the issues figured out and are ready to begin a new venture this year studying horticulture seed production in collaboration with Ball Horticultural Co.

Richard Edsall, director of seed production for Ball Horticultural, Chicago, attended the field day and visited with local growers.

“We’re looking for new places to produce seed, and the high tunnel production will be very conducive to what we are trying to do to grow flower and vegetable seeds,” Edsall said. “No one else is doing that in this area. In addition to our own production, we contract with outside growers and they can do part or all the production.”

He indicated AgriLife Research could play a role in coordinating local production and Ball would train an associate to work in this region with growers.

Knowing what to plant will be a key factor for producers who follow the research and venture into high tunnel production.

Dr. Russ Wallace, AgriLife Extension horticulture specialist in Lubbock, said after “the wind kept blowing my crops away,” he purchased a high tunnel in 2009 and he too has learned many lessons about high tunnel production the hard way – by trial and error.

The first year, Wallace said, he had two strawberries per plant, because they were planted at the wrong time. Now, he has achieved up to 2 pounds per plant, “and if you can sell them at the farmers market for $7 per pint, there’s money to be made.”

High tunnels allow earlier and later production; protect crops from severe weather and provide higher quality and quantity of produce, he said. They also allow production of some vegetable and fruit crops in what is considered traditionally a non-producing area.

“When we talk about high tunnels, we want to make sure we select the most profitable crop for the farm and for the market based on consumer demands,” Wallace said.

He said tomatoes, lettuce and strawberries are probably the top three crops grown under high tunnels. An unconventional crop is cut flowers.

“Just always make sure you have a market and a place to sell. And enough to sell,” Wallace warned. “You don’t want to make your customers mad. If you have a crop that comes in earlier but don’t have a place to sell it that can be a problem.”

He has two guides available on growing under high tunnels: High Tunnels for Crop Production in Texas and Specialty Crops for High Tunnel Production in Texas.

Dr. Tony Rho, AgriLife Research postdoctoral research associate in Amarillo, said while high tunnels protect crops, a big component of their potential success is water management. Rho is measuring water-use efficiency between the high tunnels and open-field systems using drip irrigation systems and different kinds and colors of mulch.

“We have to break down the investigation of water-use efficiency by using a physiological equation – photosynthesis over transpiration,” he said. “That is the measurement of the real-time use or responses of the plants.”

Utilizing a gas exchanger to measure the transpiration and photosynthesis both at the same time, Rho said his preliminary results show the water-use efficiency under the high tunnels is higher than the open field.

This, he said, coincides with the findings of team member Dr. Paul Colaizzi, a USDA-ARS water management research agricultural engineer in Bushland. He helped install the irrigation infrastructure, surface drip under plastic mulch beds, with different zones for research purpose.

The drip laterals are spaced the same as the beds, 60 inches, to accommodate the growth of the tomato plants and access to tend the plants. The drip emitters are a quarter of a gallon per hour and spaced every 12 inches, which works out to about 9/100ths of an inch per hour. Soil water measurements are used as a guide to schedule the irrigation timing and amounts.

He said in the soil water profile, the two limits to operate between are field capacity, or the highest capacity the soil profile allows before drainage, and a maximum allowed depletion, below which the plant will experience water stress.

Colaizzi said both tomatoes and peppers in high tunnels use less water than plants in open fields. The high tunnel air temperature is hotter, but without wind and solar irradiance of the open field, they show a little less water use. Instrumentation is used to measure the atmospheric variables that drive water use – solar radiance, air temperature, relative humidity and wind speed.

“Comparing water use in the high tunnels to water use in the fields, so far in the open fields over 47 days, the tomatoes and peppers used about 10 inches each. In the high tunnels, the peppers used about 8 inches and the tomatoes used 7-7.5 inches,” he said.

Dr. Ada Szczepaniec, AgriLife Research entomologist in Amarillo, joined the high tunnel team to establish what key insects or pests threaten the vegetable crops. She found thrips that transmit viral diseases to be the main concern.

“We are in a pickle here because we are surrounded by wheat,” Szczepaniec said. “Thrips have a broad host range and are quite common in wheat, although they are not an important pest for that crop. Every year when wheat is maturing, we see significant increases in numbers of thrips. Fortunately, we now know when this happens, so that allows us to make specific accommodations and management decisions.”

She said thrips are resistant to many insecticides, so researchers are looking at cultural practices to help manage them. One recommendation is to avoid planting tomatoes next to cereal crops, which is not feasible in the Texas Panhandle, “so we are exploring the use of UV reflective mulches instead of conventional mulches to determine whether they lower thrips numbers.

“Thrips rely on visual cues to locate their host plants and the reflective coating of these mulches may interfere with their colonization on vegetables.”

Whiteflies, which transmit diseases and are especially injurious to vegetables in the Lower Rio Grande Valley, were not as widespread as thrips, but are being monitored as well, Szczepaniec said. She is trying to determine if the same cultural practices used to manage thrips are effective in controlling whiteflies as well.

“We also have trouble with hornworms, fruit worms and armyworms,” she said. “They are tough to control and scouting for them is important. Timing of insecticide application is crucial and especially effective when larvae are still small.”

Szczepaniec added that “the goal of this entire research project is to establish an IPM-based set of guidelines to produce vegetables in a sustainable manner. We have learned from California that we have to implement an integrated control program from the start, using tactics that are as predator and parasitoid friendly as possible.”

She said the high tunnel research is a very good system to test if passive predator enticement methods are effective, for example.

The goal of these approaches is to determine “the best varieties we can grow for this region have the highly desirable agronomic traits, high–yielding fruit and some insect and disease resistance as well,” Szczepaniec said.

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