May/June 2013
Chasing Water By Dave Wilkins, Spudman correspondent

Last year’s drought convinced Colorado potato grower Harry Strohauer that he had to make a change — a big change.

He moved 500 acres — roughly half his spud production — to New Mexico for the current growing season. The farm near Clayton, N.M. is irrigated with groundwater wells.

Strohauer relies almost entirely on runoff from mountain snowpack to irrigate his farm near Greeley where he grows russets, Yukons and fingerlings.

Unfortunately, there’s no telling how much snowpack will accumulate in any given year. Too frequently, it’s not enough.

If you don’t have a secure source of water, you are setting yourself up for failure,” he said. “The drought is persisting into New Mexico too, but we have a source of water there that we can depend on.”

If there’s a downside to the move, it’s probably logistics.

“We are going to be harvesting in two different states at the same time so that will be a challenge,” Strohauer said.

This year could be another dry one for many potato farms.

Snowpack levels across much of the West were well below normal on April 1, according to the Natural Resources Conservation Service.

Spring and summer stream flow volumes may approach record lows in some areas of Colorado due to “extremely poor snowpack conditions,” NRCS officials said in an April 1 outlook report.

“We are in dire need of more snowfall,” Roger Mix, a certified seed potato grower from Center, Colo., said in early April. “It’s way too dry.”

Mix tries to make sure his pivot systems are up to date and working properly so he isn’t wasting what precious water he has.

He stopped using end guns on his center pivots about six years ago.

“We are just growing what’s under the sprinkler pattern. We don’t have any corner systems on our farm,” he said.

Mix may also increase his plantings of early maturing varieties this year in hopes of saving a little extra water.

Some San Luis Valley producers may choose to idle a portion of their farms from commercial crop production this year.

Concerned about the valley’s dwindling aquifer, a group of growers formed a groundwater subdistrict last year. Members pay a fee to join and then can bid to idle some acres in exchange for a payment. They’re allowed to irrigate the land only enough to establish a cover crop.

Growers hope the voluntary program will keep state regulators on the sidelines, Mix said. They want to avoid mandatory well shutdowns if at all possible.

Center pivots generally do a nice job of applying water uniformly, but they’re unlikely to keep up with peak water demand on a full circle of potatoes during the middle of a long hot summer, experts say.

One strategy that seems to be catching on is to plant a half-circle of spuds with a half circle of something else such as wheat or barley that uses less water.

Irrigating a 50/50 circle split is much easier nowadays thanks to modern smart panels, said Cecil Rock, former president of Pierce Corp., and now an independent irrigation dealer in Eastern Oregon.

“The newer technology is capable of handling multi applications in a given circle,” he said. “The machine will sense field position and adjust the application rate.”

A split circle can certainly make sense during a short water year, said Howard Neibling, University of Idaho Extension water management engineer.

“Growers can pull the water off the grain by mid to late July and that’s the time when the potatoes are really beginning to need more water,” he said.

Potatoes, of course, are a highly water sensitive crop and need a reliable supply all season long to ensure good quality and yield.

Spuds are particularly sensitive to water stress during tuber initiation and early tuber development, agronomists say. Too little water during this critical time can substantially reduce U.S. No. 1 yields by increasing the proportion of rough, misshapen tubers.

To avoid mid-season water stress, center pivots should be managed so that the soil profile is full at the beginning of the peak water use period (by about June 15 in Idaho), Neibling said.

He recommends that growers sample soil moisture down to about two feet after planting and put on some extra water if it’s too dry.

“You would like to go into mid June with that second foot filled to field capacity so you have that water in reserve to use on very hot days,” he said.

In Idaho, that early irrigation should be completed around the first week of June to avoid potential disease problems, he said.

Some experts recommend that excessively dry soils be irrigated prior to planting to avoid seed piece decay problems that sometimes result from irrigating between planting and emergence.

Growers should also check their sprinkler systems for leaks and replace any worn out nozzles, Neibling recommended.

“Spend some time taking care of any leaks. Those are the first places you are going to have disease popping up,” he said.

Growers should make sure that pivot sprinkler packages are up-to-date and that nozzles on wheel lines and hand lines are not worn out, Neibling said. Over time, water and very fine debris tend to wear out the brass nozzles on wheel lines and hand lines, making the orifice larger.

“If growers with hand lines and wheel lines haven’t replaced nozzles in a while, they may want to do that, particularly on systems that have some sand in them,” he said.

Growers may tire of constant reminders to replace worn irrigation equipment, but it can make a big difference.

In a 2012 study funded by Idaho Power Co., UI irrigation technicians checked wheel lines and hand lines across Southern Idaho from King Hill to Burley. The technicians measured flow rates, water distribution and other factors.

They found that on average, the systems were putting out about 10 to 12 percent more water than was needed due to leaks. Worn nozzles (and wrong-sized nozzles in a few cases) resulted in the systems putting out another 10 to 12 percent more water than was necessary.

Together, the two maintenance-related issues accounted for pumping about 20 percent more water than was necessary.

“In a short water year, that’s significant,” Neibling said.

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