Getting water to crops when they're thirstiest pays off

Wade Salo trudged through a muddy soybean field one day last month, mosquitos attacking his face and neck, carrying a soil sampler that resembled a silver pogo stick. He stopped at a metal pole bearing two pink flags atop a plastic water gauge. Sometimes, when the corn or wheat is high, he has to get on top of the old, aqua-blue pickup he drives to see the gauges he's looking for.

With a jab of his foot, Salo drove the pogo stick into the ground between the rows of loaded soybean plants and pulled up a long, narrow soil sample. He squeezed the plug of dirt in his hand to estimate its moisture content. "It's saturated," he said with the cadence of a young Paul Harvey. It wasn't surprising, given the heavy rainstorm the night before. "See, my hand is getting muddy."

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Salo is an irrigation technician for the Wadena Soil and Water Conservation District. He's part of a growing program in central Minnesota that measures rates of "evapotranspiration," or loss of water in fields, using a complex formula involving solar radiation, wind speed, air temperature and other factors.

The goal is to keep track of soil moisture levels, by the week and on a micro level, so farmers can irrigate their crops more effectively, applying the right amount of water when plants are most likely to use it.

Traditionally, farmers say they irrigate when their neighbors do or when their crops look stressed. But that can be too early or too late and result in too much or too little water. More precise irrigation saves money and grows healthier corn, soybeans and potatoes, but it also helps keep nutrients like nitrate out of drinking water aquifers, a prominent issue in this sandy part of the state where runoff--from irrigation or rain--percolates down quickly.

Called irrigation scheduling, this method of targeted watering took hold in Minnesota in the 1990s in Otter Tail County and expanded exponentially after 2005, when Darren Newville took over as district manager of the East Otter Tail Soil and Water Conservation District.

He holds the same position with the Wadena district. At that time, there were 60 or 70 fields in the program, Newville said, compared to nearly 140 in a multi-county area today. "It's a spreading idea," he said. "From Benton County over into Hubbard, Todd and Wadena counties, it's catching on a bit." He also urges farmers to switch to low-flow sprinkler heads.

This type of scheduling is more heavily used in states like Kansas and Nebraska, where water is scarcer, but its rise here shows that a growing number of people are taking steps to protect and conserve groundwater.

"Our program is reducing nitrates," Newville said.

In the Otter Tail County area, as in other parts of the state, the presence of nitrates in drinking water--which can cause oxygen depletion and a condition called "blue baby syndrome"--is of growing concern. In recent years, the city of Perham, where Newville keeps one of his offices, had to dig a new drinking water well, and nearby Park Rapids spent millions building a new water treatment plant to deal with high nitrate levels.

It's impossible to ignore the link between nitrates and farm irrigation. "There are about 10,000 irrigation permits in the whole state," Newville said, noting the area's sandy, highly permeable and often-dry soil. "Otter Tail County has about 10 percent of that, or 1,000 permits. Todd, Wadena and Hubbard counties have another 800. Twenty percent of the state's irrigation is in these four counties."

So, it makes sense that some farmers in this part of the state would embrace irrigation scheduling, said Newville. "They want to make sure they are not over-applying water to lose nitrates into the ground water," he said. "If they can prevent having to turn (their system) on, that saves them money. And if they turn it on when their crop really needs it, that helps with production. It's a win/win situation."

Salo left the soybean field and walked up onto the nearby gravel road, grabbing his laptop, which he placed on the open tailgate of Newville's cranberry red Ford F-350. He pulled up a spreadsheet loaded with data related to this 200-acre farm, much of it gathered from a custom weather station. He punched in some soil moisture information and saved the file, which he would email to farmer Andy Dombeck later in the day.

Dombeck had no need to turn on his irrigation system, by Salo's calculation. It had been a rainy summer overall, aside from a dry patch in late July and early August, and it was nearing the end of the growing season, when crops tend to use less water. "A lot of farmers are tapering off," said Salo, who has been working on this program for three years, and as a staffer since early 2013. "He's good for the rest of the season. He's done."

This is Dombeck's first year with the scheduling program, which costs farmers around $200 per year and is partly paid for by state Clean Water Fund dollars. "It's helpful," Dombeck said by phone. "It's another reference point. I can see where things are at and print out the graphs. I like data and numbers," Dombeck said. "I like to go by that instead of guessing."

The bulk of the data used to calculate evapotranspiration--evaporation plus plant transpiration, the basis for estimating soil moisture levels--comes from a series of tall, custom-built weather stations.

There are four in Otter Tail County and an additional handful that are either online or soon to be in Becker, Hubbard, Pope, Todd and Wadena counties. Precision requires multiple stations since weather can be extremely local.

Newville paid a visit to one near the Wadena airport, pointing out the various rods, canisters and whirligigs that measure temperature, solar radiation, wind speed and direction, humidity and rain. And then he opened the station's brain box, which contains a cellular modem that transmits information to his offices, where it's plugged into spreadsheets and individual farm reports.

(Some of the weather stations used to send data by telephone line, but that was more costly and gophers chewed the wires.) Once the information is enhanced and verified via in-person soil sampling, it is delivered to milk houses, mailboxes, email boxes and farm shop refrigerators.

Eventually, Newville would like to offer a cell phone app that would allow farmers to plug in their own rainfall or irrigation totals and upload the local weather station data. The app, he said, would calculate how much water they should add and "give them the chart on their phone."

Joshua Stamper, an irrigation specialist with University of Minnesota Extension, who works closely with farmers and districts like Newville's on issues around irrigation and water quality, thinks the scheduling program holds promise. "It has the potential to have real impacts on reducing nitrogen loss," he said. But it also faces obstacles. For one thing, it's hard to measure success. "One of the real challenges when you work with nonpoint source pollution is it's very diffuse," he said, noting that reduced nitrogen loss in a field doesn't necessarily equal lower nitrate levels in an underground aquifer. "Natural systems have a lot of background noise in them."

One study, from Kansas in 2005, showed that overwatering by 25 percent could lead to 16 times more nitrate leaching. "There is a greater level of knowledge about these practices," Stamper said, adding that a farmer of today probably uses 20 to 30 percent less water than a farmer of yesteryear. "A generation ago, this might have been poo-pooed and people might have said, 'That (nitrogen loss) is the cost of doing business.' Everybody acknowledges this is a major issue. All the parties involved with this are coming to the table to ask, 'How can we come up with better and better solutions to these issues?' There is no silver bullet in this. It's going to require a silver buckshot approach. Just irrigation water management and scheduling probably won't be the answer."

Though other states have more advanced scheduling systems, Stamper is impressed with what Newville and others have managed on small budgets. "It's a real burden on Darren to keep up with cataloguing and scrubbing to make sure the data is accurate," he said. "That is a real challenge to the SWCDs and staffs that really run on shoestring budgets. It's amazing they can do as much as they do with limited resources.

"They are providing farmers with a mathematical explanation of water use," Stamper said.

Sitting on the front deck of the corn and soybean farm she shares with her husband, Teresa Meemken said that after three years on the program, she has come to rely on the graphs that appear in her mailbox each week. "We just put in our first pivot four years ago," she said, referring to a center-pivot irrigator. Before that, "we had just what the Lord provided for rain. We didn't know enough... We had some good years, but more bad years. This area doesn't get enough rain."

Now, with the help of Newville and the scheduling program, "We have another backup tool," she said. "We depend on that sheet for deciding when to turn it on."

"It's easy," Meemken said. "It gives you peace of mind and you feel good when somebody is double-checking what you're doing and making sure you're doing the right thing. We could all be scientists and figure out the formula. I could probably do it, but it's nice not to have to."