New UF/IFAS research shows that reducing irrigation volume while increasing frequency can help lettuce growers save water, reduce production costs, and maintain crop yield, even under heat and drought stress.
Sandra Guzman, assistant professor of Agricultural and Biological Engineering at the Indian River Research and Education Center (IRREC), worked with scientists across the country to evaluate deficit irrigation strategies for lettuce. Their goal was simple: to help growers manage water more efficiently without sacrificing crop performance.
“The project was about finding the sweet spot for irrigation, how much water we can reduce while still protecting yield under challenging conditions like sandy soils, high vs low humidity, temperature increases, and limited water availability,” Guzman said.
Their research team evaluated a heat-tolerant lettuce variety, Manatee, with German Sandoya, associate professor of Horticultural Sciences at the UF/IFAS Everglades Research and Education Center in Belle Glade, who is a lettuce breeder.
The main question for their research was: how low can irrigation volume go without affecting yield or quality?
Florida ranks third in U.S. lettuce production, while California leads the nation. Since the research team focused on two of the country’s highest lettuce-producing states, they wanted to determine whether they could manage water in these two distinct environments, thereby developing water management recommendations for lettuce production applicable to the U.S.
“Florida is humid with sandy soils. California is much drier. These differences allowed us to look at water use across contrasting production systems,”
She said in the study they reduced it to 20% of the current irrigation water use, then tested again at 30% and 40%. They evaluated those three values in terms of crop physiology and water use efficiency.
“If you apply less water from irrigation and maintain the same yield, then you will have higher efficiency values,” she continued.
They found that reducing water use by 30% in Florida yielded promising results. Compared to California, they did not find that reduced water use led to significant changes in lettuce yield.
“We have to stop thinking about irrigation volume only, but what is the frequency?” she said. “Smart irrigation systems based on sensors and control allow the automated delivery of water at a frequency that crops require”
They hope their research can help inform lettuce breeders so they can develop varieties that are more tolerant to challenging conditions, such as those in Florida.
The idea for this project was jump-started by changes that could happen locally. Vegetable production is moving farther north toward the Treasure Coast.
“The Everglades Agricultural Area (EAA) works with mock soils, which are fully organic. The Treasure Coast region is more sandy and historically used for Grapefruit and citrus production,” she said.
She started brainstorming with Sandoya about what would happen in a case where the entire lettuce production moves from the EAA to the Treasure Coast, and what they would need to maintain and increase the competitive production we currently have in Florida.
She said lettuce crops could keep moving north due to changes in temperatures and extreme weather events.
The state of Florida might be seen as having ample water for irrigation. The issue with production in the state is that applying more water in a humid environment increases the number of pests and diseases to manage.
“There is a perception we might have excess water available for crop production in the Treasure Coast, for example, in this area, flat wood soils, are highly prone to runoff. Flatwood soils have a hard pan that restricts vertical movement. That’s why we see flooding from time to time. On top of the hardpan, we have our sandy soils, which means water that is applied in excess will move very fast and go to our fresh water sources through drainage,” she said.
One of the more important parts of their research was precision irrigation. They evaluated deficit irrigation using sensor-based technologies. It involves putting sensors in the field, which allow you to see where the water is and how fast it’s moving. Most importantly, assess if the plants are taking up water.
The sensors can also be used to set different irrigation schedules, such as every 2 days, every 4 days, or whenever, based on the plant’s needs.
“More frequent, lower‑volume irrigation helped keep water in the root zone. Even though we irrigated manually, purposely for this study, sensors helped us see how plants responded,” she said.
The main variables they looked at were physiological traits, including height, weight, leaf width, and chlorophyll content. They also evaluated nutrient content in the water, in the soil, and in the leaves and the plant. They also looked at whether the nutrients were moving with the water, and whether there was a relationship between the water you apply and the amount of nutrients and water the plant takes up.
She said deficit irrigation can work for other crops, not only lettuce.
“There is a really good body of knowledge about deficit irrigation strategies and ways to manage crops with water deficits in order to have higher production. The water quality for irrigation is important, and although it was not part of our study, it should be considered for implementation,” she said.
This research supports UF/IFAS efforts to help growers adopt sustainable, cost‑effective, and science‑based irrigation practices as vegetable production expands across Florida.
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