“Less is more” is the goal of agricultural water usage research currently underway at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS). The institution is helping vegetable farms and plant nurseries reduce water usage and other crop inputs, conserving water and improving farm profits.
Much of Florida’s commercial fruit and vegetables – such as strawberries, tomatoes, eggplant, melons and peppers – grow in raised beds, tightly covered with a thin sheet of plastic mulch, which is part of a practice called plasticulture.
Raised beds reduce flooding damage, while mulch prevents weeds and nutrient loss. Plastic “drip tape” irrigation lines run underneath the mulch. The beds are usually 6 to 8 inches tall and 3 feet wide, with two drip irrigation lines on each side of the plants.
“I wondered: What can we do to optimize this production system?” says Sanjay Shukla, professor of agricultural and biological engineering at the UF/IFAS Southwest Florida Research and Education Center in Immokalee. “Can we produce the same vegetable yield with fewer inputs?”
In 2012, the UF/IFAS researchers made vegetable beds narrower and taller – 16 to 24 inches wide and 10 to 12 inches high – by adjusting the equipment used to build the beds. The narrower bed used just one line of plastic drip irrigation tape, saving $50 to $75 per acre. Narrower beds also used less water.
“In one trial for eggplant, we were able to show reduction in irrigation volume by 50 percent,” Shukla says.
Some operations are already beginning to reap the benefits of experimenting with tall, narrow rows. Two farms, growing eggplant and tomatoes, have already switched as many as 6,000 acres to the narrow beds, with estimated cost savings from $90 up to $500 per acre.
There are benefits beyond reducing irrigation water volumes. Raising the height of the beds means less flooding risk to plants and more open area for rainfall storage, reducing potential runoff.
“This system is good for farm profitability and has environmental benefits,” says Shukla, who is continuing research with funding from the Florida Department of Agriculture and Consumer Services. “I think this system could work all across Florida for a variety of crops using plasticulture.”
Improving Container Nurseries
Researchers in the Department of Environmental Horticulture are improving irrigation in Florida’s container plant nurseries. A 1-acre nursery may contain 10,000 to 20,000 three-gallon containers, which are irrigated daily.
“That uses a lot of water,” says Jeff Million, research associate. “In the past, operators often just ran water using timers. Our main research goal was to provide a more objective way to irrigate.”
The UF/IFAS container irrigation management program, or CIRRIG, divides a container plant nursery into different zones, with a weather station collecting weather information on site. The CIRRIG program combines the weather data with plant information – like plant variety, leaf canopy space and container size – to calculate evapotranspiration, or the amount of water used or lost by the plants.
CIRRIG then calculates actual water needs and irrigation time adjustments. The operator can make those adjustments, through a web-based system, using programmable irrigation microcontrollers in the nursery.
“We adjusted irrigation times out in our test site from the office on campus in Gainesville,” Million says. A six-month trial with CIRRIG showed a 21 percent water savings in a side-by-side test of sweet viburnum in containers. Accounting for rain, temperature and plant specifications, water savings with CIRRIG could reach 40 percent for some nurseries, according to the UF/IFAS report.
There is a financial cost.
“This equipment is sophisticated,” Million says. “It may not be for everybody. But people with higher pumping costs could benefit.”
One large nursery using the system calculated savings nearing $100,000 – enough to offset equipment costs.
There are other benefits, too.
“Overwatering can result in poorer plant quality, so this system helps prevent those losses,” Million says. “And it could help reduce the amount of fertilizer and pesticides needed.”
That’s good news for container plant nurseries, which usually operate on low profit margins. “Even saving a few dollars really makes a difference,” Million says.