New system for lettuce traceback and improved yields

Photo courtesy of Timo Balk/

The lettuce industry is of major importance to the southwestern economy. New technology coming out of the University of Arizona can contribute to this economy by giving growers more tools for precision production management and, at the same time, increase the traceability of food, contributing to food safety management. Kurt Nolte, UA agricultural agent and regional specialist, said, “This system is highlighted with the seamless traceability of produce from the retail shelf back to precise grower protocols.” Nolte and research colleagues at UA Yuma County Extension have been working with ways to improve lettuce yields while at the same time providing an efficient traceback system that can be crucial should an event occur whereby produce is contaminated.

A system is currently being tested in local head lettuce production fields. The system initially tested in early 2009 provides not only field-level tracking of iceberg lettuce, but also site-specific yield determination, a significant issue as growers work on an increasingly tight profit margin. Potential exists for the system to be developed for use in other crops harvested in a similar manner and is extremely important to growers as overhead costs and competition increase, thereby requiring increased production efficiency. Precision production techniques gaining use in row crop production must make their way into produce growing to help growers continue to produce food with an acceptable profit margin.

Lettuce moves across lettuce harvest aid equipment after being cut in the field.
Photos courtesy of Kurt Nolte, unless otherwise noted.

The system differs from existing traceback systems in that it offers capabilities to incorporate field information that can lead to improved yields based on soil or water information from specific areas of fields.

Lettuce production

While most of the U.S. lettuce production is in California, 100 percent of the winter lettuce production is in southern Arizona, in the Yuma area. Arizona’s agricultural production is about a $9.6 billion industry, and lettuce represents $2.4 billion of that total, in the range of one-third of the total agricultural production dollars. Although a decline in iceberg lettuce in the U.S. has occurred over the past 10 years, other lettuce varieties have gained in popularity.

Lettuce harvesting has changed tremendously since the 1950s, when workers moved through fields harvesting heads of lettuce into bins that were transported to packing sheds. Most lettuce packing today is done in the field, with lettuce packed directly into cardboard cartons, exhibiting an assembly line system as harvesting equipment and workers move across fields.

Despite technical improvements contributing to that assembly line system, lettuce continues to be harvested by hand. A harvest aid machine is used to help workers harvest the lettuce efficiently. The lettuce is cut by hand and laid on a chute on the harvest aid machine where other workers wrap the heads of lettuce in plastic wrap and place them into cartons. Cartons are placed on conveyor belts before being loaded onto pallets and transported to cooling facilities.

Although yield information is collected, current yield information has not been specific to small areas within a field, where production issues may occur related to soil or water. While the risk of contamination is present, consumer demand for minimally processed produce has increased. In response to this risk, various tracing systems are present to track food back to the production site. Some systems allow more specific traceback than others.

A worker on the harvest aid equipment wraps lettuce for placement into cardboard boxes.

System design

The recently developed UA system can trace carton-level, packed iceberg lettuce to an exact field location. The system uses radio frequency identification (RFID) and global positioning system (GPS) technologies to track specifically where the lettuce was picked. In addition to contributing to reducing illnesses from contaminated food, the system can help reduce devastating effects on growers that occur during a lengthy search for the site of contamination. Should such contamination occur, avoiding the economic impact on growers that has occurred in recent years in tomato and spinach production is a major breakthrough. A harvest aid machine will allow producers to identify the yield of specific areas, enhancing their abilities to address fertility or irrigation issues in their fields.

A remote electronic carton tracking field management system includes a field unit. Georeferenced harvest data is sent wirelessly to a base unit. Several pieces of equipment are involved, including a satellite receiver that collects microwave signals from the GPS satellite network and communicates geocoordinates to a field computer. Computer RFID identification integration links these geocoordinates with crop information that has been input into the system. The remote field computer serves as a crop harvest and field history data storage device. Carton and field history data is received for management and storage and made available to Internet users or used later for harvest yield operations.

Nolte said, “Essentially, the system was fix-mounted within a harvest aid machine, with the antenna attached to the wings of the unit and hardwired to the RFID encoder.”

Field workers sign into the system on a computer before they pick and pack the lettuce into the cartons. Field information on the RFID labels includes shipper/grower, crop, crew members, weather conditions at harvest and other growing parameters that have been selected. The information contained will allow later identification of not only the specific location where the lettuce was picked, but also the identification of the worker who picked the lettuce. The information also facilitates identification of other lettuce picked by that worker in adjacent locations.

RFID antenna and label are attached to the lettuce carton.
Packed boxes of lettuce are palletized.
Tracking system equipment includes a computer, GPS and RFID encoder.

Field testing

Nolte said, “The system was field tested with a local grower on three head lettuce fields. We pre-labeled 5,000 field cartons with RFID tags and integrated them into the harvesting operation. Although the lettuce carton tracking system is currently available and used in similar inventory management, the integration of real-time GPS into RFID technologies makes this approach unique. ”

Georeferenced field cartons were used to provide the first site-specific yield evaluation of produce within the industry. This facet of the system can provide the grower with increased tools to increase profitability of production. In one of three fields evaluated in the testing, lettuce yields ranged from 700 to over 800 cartons per acre. This wide range of yields represents a major profit difference to growers, and causes of the variance can be identified and addressed with this information.

Other crop potential

Nolte said, “The system integrates field-level crop attributes and GPS coordinates into each carton while improving food security and efficiency of the agricultural food supply chain. The lettuce carton traceback system shows great potential for tracking many crops harvested into cartons.”

The system allowed researchers to provide growers with various information related to their production fields. This information was used to focus on ways to improve yields in specific areas where yields had been low. Information will continue to be collected to evaluate the effectiveness of specific improvements aimed at improving yields.

Nolte cited the system’s ability to trace back with visualization tools the entire movement of lettuce from the grocers’ shelf to the field of harvest. These capabilities become increasingly important as the nation focuses on bioterrorism prevention and growers continue to look for ways to not only increase their food safety and marketability, but also to assure that they may continue to operate profitably.

Funding for the development and testing of this technology was provided by the Arizona Department of Agriculture.

Nancy Riggs is a freelance writer and frequent contributor to Growing. She resides in Mount Zion, Ill.