Farm Horizons, Aug. 2016

A better way to water crops

By Gabe Licht

The Hasty area is known for its truck stop. That area is also becoming known for something else: a different way to water crops.

Just a little more than a mile northeast of the landmark along I-94, Wright County Farmers of the Year Russ and Sharon Martie have implemented subsurface drip irrigation on 39 of the 400 acres they farm, with hopes of doubling their yields, and plans to implement the system on another 14 acres – currently serving as a control field – in 2018.

What is subsurface drip irrigation?

“With subsurface drip irrigation, we’re putting a water-conducting tube in the root zone,” said Scott Wicklund, of Minnesota Irrigation Distribution Center, who designed the system. “We’re delivering water right to the roots so there’s no run-off, wind drift, or evaporation before it can get into the ground.”

It starts with a 195-foot deep well.

“It pumps out about 260 gallons per minute,” Russ Martie said. “That goes through a sand filter because you don’t want sand to plug up the holes.”

Martie uses solenoids to open the valves that sends the water to PVC pipes and, ultimately, to the tubes – also called tapes – that go out into the fields a foot underground and 51 inches from each other, using a rig Martie built for $1,200 using a chisel plow he found at a junk yard.

“Every two feet there’s what I call a weep hole,” Martie said of the tapes.

That’s enough to provide the appropriate amount of water to all the roots.

“Ideally, you’re not trying to get a tube under each row, but let the soil move the water laterally,” Wicklund said. “The more water in it, the more lateral movement you’ll get, just like a sponge. The heavier the soil, the further it will go laterally. Even in light soil like what Russ has, it still moves considerably side-to-side. He’s worked organic matter into it over the years, too. That improves the lateral movement he’ll get.”

It takes 4.7 to 6.6 hours to apply a quarter inch of water to each field.

Martie uses moisture sensors at 8, 10, and 12 inches to help determine when water is needed.

“We take the temperature and moisture every day,” Martie said. “My wife records it, puts it in the computer, and the computer tells us when to water. Right now, we’re at a 15 percent deficit. If it gets to 30 and 40 percent deficit, it tells you to irrigate.”

Bubbly water

Martie has added a new feature to the irrigation system on his smallest field.

“What I’m doing on this field, I’m injecting microbubbles with a venturi valve,” Martie said. “You don’t want big bubbles because they’ll rise to the top and become one. You want microbubbles so there’s thousands of bubbles in the water.”

For Martie, the reason to do so is simple.

“What are the two most important things for a plant to grow? Water and oxygen,” Martie said.

Martie referenced success Egyptian farmers have had by introducing more oxygen to their plants using microbubbles.

“They had two acres of tomatoes. One, they put subsurface drip irrigation in. The other they put subsurface drip irrigation in it and injected air,” Martie said. “The field that just had subsurface drip irrigation raised 15 tons of tomatoes in an acre. The field that they put air with? Thirty-three tons.”

Martie is hoping for similar results as he aims for 200 bushels of corn per acre on land that routinely produced 80 to 100 bushels per acre before.

Even before he added the venturi valve, yields were trending that direction despite a problem with the well, which has since been corrected.

“Last year, I did get 150 bushels per acre on a 10-acre field, and on another field I got 175 bushels per acre,” Martie said. “I kind of limped through last year, and should be able to do it better this year because I can control it better.”

Advantages over center pivots

“The impetus for this is water conservation,” Wicklund said. “The main way it conserves water is that 100 percent of that water becomes available for the roots.”

Martie said his system uses 40 percent less water than a center pivot.

His moisture sensors allow him to monitor how much water is needed.

“It allows us to more efficiently use our water,” Wicklund said. “If we’re seeing moisture increase below the root zone, that’s not good. We can monitor that, and more efficiently time our irrigation.”

Saving water and electricity also saves money.

“The other thing we’re showing is energy consumption because we don’t need as big of a pump station because it’s delivered at lower pressure,” Wicklund said. “The energy consumption on subsurface drip irrigation versus center pivot, even in a year like last year where it rained every third day, the energy consumption was considerably less.”

For example, Martie compared his son’s electric bill of $108 for a field with a center pivot to his electric bill of $40 for a similarly sized field.

Wicklund noted that subsurface drip irrigation is ideal for smaller and irregularly shaped fields.

“A big, square field of 80 acres or more is perfect for a center pivot,” Wicklund said. “Once you get into irregularly shaped fields and smaller fields, it’s not feasible. That’s another area where this technology shines.”

Martie believes that some fields that could not accommodate a center pivot and are not currently being farmed could be farmed successfully using subsurface drip irrigation.

In addition to applying water and microbubbles through subsurface drip irrigation, Martie also applies fertilizer.

“I set a meter to what I want, set my timer, and I have a fertilizer pump that injects fertilizer right to the root system,” Martie said.

Being able to add fertilizer in the summer is key.

“You know when a plant gets up to the eight- to 10-leaf stage, it uses 75 percent of the fertilizer,” Martie said. “I’m going to put it on through the water. I’ll probably come over every three days and get the fertilizer put on. I really don’t need the moisture right now. I just run the moisture to carry the fertilizer.”

To do so, he only needs to run the system for about 2.5 hours, compared to about twice that long when he is watering.

Wicklund believes Martie’s techniques will prove to be effective and efficient.

“We’re hoping to be able to show by putting it right in the root zone and being able to apply it right when the plant needs it, spoon-feed application rather than broadcast application, that it can increase yields,” Wicklund said.

Introducing fertilizer in the root zone prevents runoff and also keeps it from entering the aquifer.

Challenges

Subsurface drip irrigation does not come without its fair share of challenges.

Josh Stamper, an irrigation specialist with the University of Minnesota Extension, said it can be difficult to utilize subsurface drip irrigation in light soil.

“Where it has worked really well you have heavy- to medium-texture soil,” Stamper said. “Most of the irrigated sands in Minnesota are light-texture. When you bury the drip lines, it’s hard to pulse the water to drive it up.”

It can also be challenging to determine how deep to bury the lines and how widely to space them to meet the demands of the crop, Stamper said.

Burying them too deep could cause a problem.

“When you place the source of irrigation below the soil, it’s hard to overcome the gravitational pull,” Stamper said. “How do you make it work in course-texture soil, where it’s hard to pulse water up into the profile?”

Martie and Wicklund worked together to answer that question and find the “sweet spot,” Stamper said.

Another challenge occurs for farmers who want to use subsurface drip irrigation, but don’t want to use no-till or low-till techniques.

“You have to use GPS to make sure you’re not tilling where the tapes are,” Wicklund said. “It can be done, but it’s another level of complexity and another expense that a smaller operator may not be set up for. Looking at the sand plains north of the metro, a lot of that is conducive to no- or low-till.”

That’s the system Martie utilizes.

“You can’t take a chisel plow to it,” Martie said. “I do minimum till. I use a disc and go down 4 to 5 inches.”

An example for others

Martie received a grant from the U of M Extension and another from the Farm Service Agency which require him to compare subsurface drip irrigation to no irrigation and a center pivot.

He has opened his farm up for local farm field days, including a July 21 event, and even hosted some women from the eastern European country of Moldova.

“Russ’ farm is a demonstration,” Stampler said. “He’s been blazing a path toward this. I view what he is doing as a great way to get people excited about new technology that warrants more exploration.”

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