There is clearly a lot of interest in subsurface drip irrigation (SDI) in the western alfalfa industry based on the worsening drought and the large turnout of growers and other industry members at a three-hour workshop held in December.

Instead of hitting the road near the conclusion of the California Alfalfa, Forage, and Grains Symposium held in Long Beach, Calif., several hundred growers and other industry members stayed glued to their seats to learn the pro’s and con’s of subsurface drip irrigation in western-grown alfalfa.

“Less than 2 percent of California alfalfa acreage has subsurface drip irrigation,” said Dan Putnam, University of California Extension specialist. He estimates that total SDI alfalfa acreage in the Golden State is a maximum of 20,000 acres.

According to an industry source, California alfalfa acreage totaled about 875,000 acres in 2014.

Why the interest in spoon-fed water through SDI to alfalfa roots versus traditional flood irrigation? Putnam points to the ongoing ‘water squeeze’ (drought) in California, fairly flat alfalfa prices, higher yield potential, and the limitations of flood irrigation.

Water uniformity

Some growers using SDI report a 2.5-ton- per-acre increase over flood. A key reason, many of the SDI workshop speakers noted, was the superior water distribution uniformity which SDI delivers.

To justify the costs of SDI in alfalfa, Putnam says yields must increase. He estimates SDI installation costs in general at $1,800-$3,000 per acre depending on the life span of the system.

According to Putnam, the advantages of SDI include ‘spoon feeding’ water, fertigation, an ability to irrigate close to harvest, labor savings, zero runoff, and providing more oxygen to the root zone.

Drawbacks, he says, are SDI installation costs, pocket gopher damage as rodents love to chew on plastic irrigation parts, energy cost requirements to operate the system, maintenance, filtration, and reduced wildlife habitat.

“Growers must be prepared for a higher level of management, particularly with gophers,” Putnam said.

Rodent control

Eduardo Currea told the crowd that effective rodent management is essential for successful SDI use in alfalfa.

“There is no single answer to effectively control rodents,” said Currea, general manager of Ag Water Chemical in Fresno, Calif. “It requires an integrated approach that requires planning.”

This approach can include habitat modification, baiting, trapping, fumigation, and other methods.

Currea has 20 years of previous experience in drip irrigation with Netafim USA and Rainbird Irrigation. He says rodent damage results in an estimated 8-percent yield loss on average with SDI.

Before installing an SDI system, he urges growers to do their homework.

“If you have a field on your farm with a rodent problem, you should install SDI in another field,” Currea said.

Habitat modification includes mechanical deep ripping of the soil, weed and food source removal, and creating buffer zones around the field.

Baiting efforts, Currea says, usually deliver about 40 percent efficacy. He says baiting the field perimeter is a good idea.

Currea believes trapping, including uncovered traps and pinchers, works better than baiting.

“If the traps are not working - move them,” Currea suggested.

Biological control

Biological controls can also be effective in rodent control. One owl can consume 150 rodents per year. Place one owl box on every 10 acres.

Currea also advocates use of the product Protec-T which uses a unique smell applied through the irrigation system. He says Protec-T has been up to 90 percent effective when used with other gopher control methods.

If rodents are not controlled, SDI repairs can cost $200 per acre annually.

Patrick Fernandes of Netafim USA discussed SDI irrigation system design in alfalfa.

“It is essential to understand soil types and subsurface water movement through the soils to design the proper components for a system,” Fernandes said.  

Dripper line depth placement should be 8-12 inches deep in sandier soils and 7-10 inches deep in heavier soils, he says. Placement less than six inches deep is not recommended with SDI.

With drip lateral line spacing, the goal is to create a blanket of water across the field using capillary action to move the water. Spacings of 30-40 inches are common for growers.

Fernandes said, “The key to the SDI evaluation process is to seek out qualified people to help evaluate your soils and water quality.”

Increased yields pivotal

Todd Rinkenberger of Netafim USA said SDI is all about increased yields. Some tomato growers who have adopted SDI report yield increases from 45-70 tons per acre annually.

He says a 20 percent yield increase over flood-irrigated fields is average for SDI. Some tomato growers have seen 35-40 percent yield improvement which Rinkenberger says comes largely from uniform water applications.

He showed two slides which suggest the monetary payback for SDI in alfalfa takes about 2-2.6 years.

“Even if hay prices fall to the $225-$200 per ton level, SDI is still a good investment,” Rinkenberger said.

On the university side, Daniele Zaccaria is a University of California, Davis Cooperative Extension agricultural water management specialist.

He echoed the points made earlier about the importance of an even distribution of water water to the roots. Forty-inch spacing is the most common spacing in commercial uses but he said it may not be the best.

“My question is if 40-inch spacing is not the best - then what is?” Zaccaria asked.

Grower success

Discussion shifted to a panel of three California and Arizona alfalfa growers who utilize SDI in alfalfa production. The growers included:  John Summers, ACX International Ag Management in California and Arizona; Russell Schafer, Wegis and Young, Buttonwillow, Calif.; and Nico Slabber, Lone Oak Dairy, Hanford, Calif.

Summers’ experience with large-scale SDI began on a previous farming operation he managed in 1996. Today, he says ACX has 3,000 acres of SDI alfalfa in the Imperial County and central Arizona low desert areas.

For ACX, the predominant soil type in SDI-installed areas is sandy loam with a dripline depth of 11 inches. Dripline spacing is 40 inches.

Irrigation is typically started four days after harvest and stopped several days before harvest, says Summers. The average hay yield is 14 tons per acre per season.

He says SDI offers other perks including increased stand longevity.

While the stand longevity of many flood-irrigated fields in the West overall can average 3-5 years, SDI use by ACX delivers a 7-9 year stand life. Yield decline usually starts in the eighth-to-ninth year.

Wegis and Young experience

According to Russell Schafer, the Wegis and Young farming operation installed SDI in 2013 on 81 acres of alfalfa grown in clay loam soil in Kern County, Calif. The dripline depth is 12-15 inches with line spacing at 38-40 inches.

Schafer says yields can vary due to many factors yet yields totaled 12 tons of alfalfa per acre the first year after SDI installation.

“Our level of (SDI) satisfaction is 8 out of 10,” Schafer said. “The most important benefits are the reduced labor costs and increased yields.”

At Lone Oak Dairy in Kings County, Calif., the operation has 80 acres of SDI-irrigated alfalfa in clay loam soil installed in 2012. The dripline depth is 14 inches with 40-inch line spacing.

In the first years after installation, hay yields were 13-14 tons per acre per season, plus a significant reduction in water use compared to previously flooded fields.

Slabber gives SDI in alfalfa a ‘9 out of 10 rating.’

“Our highest concern is gopher issues,” he said.

After each irrigation, fields are checked for rodent damage and leaks. Dealing with gopher issues can cost about $120 per acre annually.