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drip irrigation lines dropping from a center pivot Courtesy of Dragon Line
DROPPING WATER: Dropping drip irrigation lines from a center pivot offers water-saving benefits that are being researched by Kansas State University.

Digging in on mobile drip irrigation

Turning a pivot to a drip irrigation system offers advantages over spray systems.

When you talk to Monty Teeter, there’s one point he really wants to get across — mobile drip irrigation is drip irrigation; it is not a new kind of nozzle. His company, Dragon-Line, is working to make the concept of mobile drip irrigation more common, but he’s still answering a lot of questions.

“We coined ‘mobile drip irrigation,’ or MDI, to go with ‘subsoil drip irrigation,’ or SDI,” he told a group during the Irrigation Show in Las Vegas earlier this month. “This is a drip system. It works different than a spray nozzle.”

Irrigation country is dotted by the circles of center pivots, and over the years, irrigators have worked to reduce water use. From the old high-pressure days to new lower-pressure systems and the use of drop nozzles and wobble heads, producers are working to get water to the crop while maximizing water use.

Mobile drip irrigation brings the water right to the soil. “With MDI, you eliminate air loss of water, canopy loss, surface loss and deep loss,” said Jonathan Aguilar, associate professor and water resource engineer, Kansas State University.

When MDI made its debut in the country, farmers started asking questions, so K-State embarked on work to evaluate this new way of delivering water to the plant. The research is ongoing, but Aguilar found some interesting benefits to the system. For example, he found that MDI provided 35% less soil water evaporation before the canopy closes, versus in-canopy spray nozzles.

“MDI has the lowest runoff potential,” he added. “You drag that pipe through the crop, and you redistribute along those areas in the field where you have the lowest potential for runoff,” he said. “Another thing we weren’t expecting is, the soil moisture profile at the end of harvest shows more soil moisture with MDI than with spray — almost an inch more water in the soil profile.”

Aguilar has been researching MDI on several test farms in Kansas, and the work continues. In 2018, yield trials showed that spray application of water outyielded MDI on a per-acre basis, but water use efficiency was higher for MDI. For example, spray application of water provided 18.5 bushels per acre-inch, while MDI provided up to 24.8 bushels per acre-inch of water. “With reduced well capacity, the [MDI] system outshines the spray,” Aguilar said.

There are still some issues Aguilar said he’s looking at, like management of the system compared to conventional sprayer systems. There are concerns about grazing in the fields with MDI, and issues with driving across fields. He continues his research.

Farmers talk benefits

Teeter, with Dragon-Line, arranged a panel of farmers and agronomists to address attendees at the event. He opened with a discussion of the key features of MDI, and the factors that farmers should consider to maximize the system, including filtration and water treatment to keep lines clear.

As for the investment, he explained that this depends on what flow you have for each field and the type of water you’re using. “The cost can range from $200 to $400 per acre,” but $400 would be real extreme, and this is a one-time cost,” Teeter said. That’s significantly lower than installing subsurface drip irrigation, and many farms already have pivots at work.

One issue is length of the drip lines, which must stagger across the length of the pivot. Teeter said they work with lines from 1 foot long (on the surface) to 100 feet long, on 60-inch spacings. The top length for 30-inch spacing is 50 feet.

The drip lines now use pressure-compensating emitters that are self-flushing, to keep lines clear. “We adapted the hoses to different designs and hookups,” he said. “We’re not using sprinkler heads or pressure regulators anymore, although we do have some options where the spray head is available to help with germination.”

Jacques Willemse, a third-generation farmer from South Africa, sat on the panel and was a staunch advocate for MDI. He noted that return on investment for the system may be hard to pin down, but said “Our production is up, quality is up, disease is lower, the wheel tracks are gone, we’re seeing less wear on equipment. … As a farmer, it’s the next best thing to farming since the tractor took the place of the horse.”

Willemse said he changed his farm from 45-kilowatt pumps to 11-kW pumps, too, cutting his power needs to pump water to the system.

One factor that’s becoming evident for MDI is the need to plant circles in circles, rather than rows. This improves the flow of tubes through the crop. But it is a change many farmers will want to review.

Willemse noted that he’s long planted in circles in his pivots, so the change wasn’t a big deal to him. “And you don’t have to do all the turns and backing up with the planter,” he added.

The dry wheel tracks may be a surprise benefit to farmers looking at MDI. You’re placing the water on the ground; it doesn’t flood wheel tracks, which keeps them drier, which does reduce wear on gearboxes.

As for disease pressure, Willemse noted that you’re putting water on the soil for roots, not on the crop, — which creates a wet environment, where disease can be an issue.

Teeter added that the on-the-soil application method is also popular in some specialty drops like mint, where irrigation can dilute oil content in the plant.

You can learn more about the concept by visiting dragonline.net.

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