Going Underground: Irrigation Breakthroughs in Drought-Stricken California

Recent years of record-breaking drought and heat have caused many agricultural producers to rethink operations. Flood irrigation has been one of the biggest casualties, often being replaced by subsurface irrigation (SDI). Yet, while the switch decreased the use of water from stressed aquifers, it created another challenge altogether for many dairies—what to do with effluent previously applied via that same-said flood irrigation.

For dairies, effluent is a readily available fertilizer. It hasn’t been practical, however, to apply it in SDI, mainly due to the risk of it clogging the underground lines. Instead, dairies still in need of fertilizer purchased synthetic varieties that can be applied through drip; this, while the manure water threatened to become a liability as lagoon levels began to rise.

Nate Ray, De Jager’s farm manager.

Recently, though, a test of new SDI technologies at De Jager Farms, a 17,000-acre operation, supplying feed to some 25,000 dairy cows in the Golden State’s Central Valley, has shown promise. Working with drip-irrigation pioneer Netafim and Sustainable Conservation, a nonprofit organization focused on environmental concerns, De Jager has hosted the pilot project for the past two-plus years, testing proprietary technologies that monitor the electrical conductivity of the effluent and automatically maintain the concentration of fertilizer.

According to those involved with the project, no such trial has been able to apply effluent via SDI in a commercial way. Until now.

Results

It’s been an auspicious beginning, say those involved in the study, in which effluent was applied via SDI in a 40-acre field of corn. An adjacent 40-acre control plot received a synthetic fertilizer, which was also applied via drip tape. Not only did the use of on-farm nutrients eliminate $200-plus in synthetic fertilizer expenses per acre, the field with effluent applied in SDI showed yields 25 to 30% greater than the control plot.

Says Nate Ray, the De Jager farm manager, there’s not only more crop per acre, the corn is also higher quality. In addition, consider that crops grown with SDI, with or without effluent, require some 30% less water than flood irrigation, which, again, has historically been the practice of choice for many dairies in the Central Valley and elsewhere.

Too Costly Not to Proceed

About six years ago, De Jager’s North Dairy (in addition to the farm, the De Jager family has eight milking facilities) began installing SDI in several of its farm fields. The unit, which houses 3,000 cows, now employs SDI on some 1,000 acres of land planted in corn, wheat and alfalfa. Ray says he hopes to install even more, but has been waiting for several reasons, including results from the effluent test.

The recent drought, however, has made the expansion of SDI and the effluent test all the more critical. “For the last four years,” Ray says, “we’ve been in the midst of one of the most historic droughts. The drought and the subsequent heat that’s come with it, it’s basically put a real strain on our water supply. We’ve been relying 100% on our groundwater sources, and with so much pumping, we keep lowering this water table.”

In addition to depletion of groundwater, concern over nitrate runoff—due to, for instance, the inefficient application of effluent via flood irrigation—helped get Sustainable Conservation involved. As a result, the organization was actually the instigator, suggesting the test project to the De Jager family and Netafim, both of whom were already working together on standard SDI implementation.

“De Jager Farms is a very innovative farming operation, always working to the future and always a leader,” says Ladi Asgill, the senior project manager with Sustainable Conservation. Netafim, he notes, is one of the world’s leading drip irrigation companies, always looking to, he says, “push the boundaries and develop new solutions.”

A Greater Sense of Urgency

Project participants knew the test would face a variety of hurdles. One was the potential for clogging. Even when using non-effluent water, suspended and total dissolved solids must be filtered before water enters lines. Dairy effluent adds another family of substances—biological particles—that can clog, as well as foul those lines.

Ladi Asgill of Sustainable Conservation and Netafim’s Dennis Hannaford.

“Your cost of treatment … is going to be higher on a dairy waste system than it is on other systems,” says Dennis Hannaford, product application specialist for Netafim. “That’s simply because we have to deal with all three of those aspects of water treatment.”

The ever-changing nature of lagoon water itself also presented a challenge. “Dairy lagoons are like moving targets,” says Ray. Based on a variety of causes, “they change as far as the concentration and basically the viscosity of the manure water. So every time that you go to start up, you’ve got to check your product, see actually what you’re injecting.”

Another problem highlights the urgency of finding means to use less water sooner rather than later. As groundwater continues to be depleted, as Ray noted is the case at De Jager, wells must be dug deeper, often causing more sand and other particulates to enter the irrigation stream.

“There was a widespread belief,” says Asgill, “that because of the … suspended solids in liquid manure, it was going to be a very challenging endeavor. But probably, after the first year, we realized that the application of liquid manure was not so much of a problem going through the emitters and the drip tape, it was the sand … from wells because of the drought and the declining water table.”

Hannaford agrees: “By heavy pumping of our groundwater, we started getting more and more sand coming out of our … deep well.” As a result, he says, particulates in the system went from 3 parts per million to 45 parts per million.

The solution, according to Hannaford, was to add five more horsepower to the system to operate an additional sand separator. Adding the latter to the line prior to groundwater mixing with lagoon water did the trick.

Success and Next Steps

The pilot required considerable efforts of all involved and, says Hannaford, “substantial testing” of everything from the state of the lagoon water, filters and the water emitted from the drip tape. Looking into next season, Netafim plans to add three or four similar systems to other area farms, and a possible commercial launch in 2017. As for De Jager Farms, which also grows some almond and specialty crops, Ray believes he will expand the project into additional acreage. He also hopes to increase the percentage of effluent running in the tape to about 50%; during the test, the mix was approximately 80% fresh water.

The bottom line, he says, is that he believes the system will pay off. His experience with his non-effluent SDI systems is that they have “generally paid themselves off in three to four years … I would say this system [is] probably going to be closer to five to seven years, just because we’re going to have more money into the filtration side of it than we are on just a conventional subsurface system.” All three of the individuals interviewed for this article also believe there are benefits beyond the farm itself. One is a reduction in nitrate runoff, in part because the fertilizer will be applied closer to root systems.

Water conservation is another benefit. “We have a very limited water supply that we’ve got to manage,” says Hannaford. “If we don’t manage that effectively in the future, we’re not going to have the freshwater supplies that we need to continue to grow the food that we need, let alone to survive.”