Under the Gun
Technology Helps Farmers Decide How to Best Use Limited Water Supplies
Roric Paulman, Sutherland, Nebraska, is under the gun -- the irrigation gun, that is. Paulman and his 24-year-old son, Zach, farm 5,000 acres in the Republican and Platte River basins of southwestern Nebraska. The Cornhuskers grow 11 different crops under pivot systems. Corn is their main crop.
"My livelihood is irrigated agriculture," says Paulman, who has served on the Nebraska Water Sustainability Task Force.
Water is like gold for farmers in Paulman's area. Republican River water, in particular, is the center of a sometimes contentious, decades-long discussion between Nebraska farmers and those in neighboring Kansas. A pact reached in the early 1940s between the two states and Colorado limits the amount of basin water (surface and pumped) Nebraska farmers can divert for irrigation. The limit helps assure adequate water reaches Kansas farmers downstream.
The modern-day upshot of the pact is an intense effort to stretch each gallon of irrigation water. Paulman has turned his farm into a giant demonstration plot for variable-rate irrigation (VRI). He estimates VRI saves 2- to 3 acre-inches of water annually across the fields where the technology is used. An acre-inch is the amount of water it requires to cover 1 acre with 1 inch of water, or about 27,200 gallons.
SYSTEMS APPROACH
"We don't shoot for maximum yields. What we really want to know is water used per bushel," Paulman says.
The family's yield average in 2012 for irrigated corn was 203 bushels per acre without VRI. In 2014, Paulman's second year with VRI, early harvested fields averaged 225 bushels to the acre.
Paulman says he can't say how much of his increased yield comes from variable-rate irrigation and how much yield increase comes from other water-conservation practices he started at the same time.
MULTIPLE TOOLS
VRI is just one part of his water-management package. He also uses variable-rate seeding and fertilization, seed treatments, strip tillage, moisture sensors and in-field weather stations.
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Paulman uses "speed-control" VRI on most of his pivots. He did install "zone control" VRI on a 130-acre field that produces high-value crops, such as black beans, sugar beets and yellow popcorn.
Speed-control VRI irrigates fields in pie-shaped sectors. Depending on the VRI prescription, the unit speeds up or slows down to achieve the desired application depth along a sector.
Zone control is more precise than speed-control VRI. But it is more expensive for the additional hardware, such as control valves for each sprinkler. Zone control can be used to turn off water (for ditches, canals, wet areas and other areas you don't want watered) or change irrigation rates for specific areas.
Paulman can vary the water rate over 5,000 segments (zones) with his zone-control VRI system. He currently has the system programmed to vary the application rates on 2,000 segments. Soil and slope variations make this system appear, at least initially, like an attractive water-management tool.
To help his customers manage water, Ian deWaal uses speed-control VRI. Based on an uploaded VRI prescription, the pivot speeds up or slows down to achieve a desired water-application depth. DeWaal says VRI saves 3 acre-inches of water per growing season on his irrigated fields. The 34-year-old entrepreneur, from northwest Kansas, farms with his wife, Michele. They also are Valley Irrigation dealers and CropMetrics representatives. CropMetrics specializes in prescription farming.
CONSISTENT PRODUCTION
"The neat thing is we're not wasting water with overirrigation or runoff," deWaal says. "[But] the main benefit of VRI is keeping yields consistent in spite of dry growing seasons," he says. In the drought years of 2012 and 2013, the deWaals maintained corn yields at their historical farm averages. In 2014, which was a better growing season, yields were 15 bushels per acre above the historical farm average.
DeWaal says the best yield he ever harvested from one field was 215 bushels per acre. Using variable-rate irrigation on that same field, he recorded a yield of 232 bushels per acre. But he applied 6 inches less water than his five-year average. This saved $6,000 in water-pumping costs.
CropMetrics uses soil-moisture probes in conjunction with VRI to make updated irrigation recommendations to customers through emails and texts. Farmers pay CropMetrics about $6,000 per pivot for equipment installation and a license agreement in the first year. In following years, the farmer pays $1,400 annually per pivot. The deWaals have 3,600 acres of farmland under management.
"I believe this technology will one day become as big as auto-steer for tractors," deWaal predicts.
Chad Lindau, Hildreth, Nebraska, runs nine pivots over 1,000 acres of corn and soybeans. Most of Lindau's land is 20 miles from the Republican River, but he still faces some water restrictions even though he is not pulling water directly from the river.
"I've tip-toed my way into prescription farming over the past few years with variable-rate seeding and fertilization," Lindau says. "VRI is my final step in matching water rates with seeding rates and fertilization rates."
IMPROVED EFFICIENCY
Some of Lindau's pivots can't make full circles because of obstructions. They run in a "windshield wiper" pattern, which creates a watering overlap as the pivot returns over ground just recently treated. VRI helps to eliminate the problem. After limited experience with VRI, he estimates he saves more than 1 acre-inch per year.
"In years when water is short, every drop of water is worth a lot," Lindau explains. "I'm afraid our water situation isn't going to get better anytime soon."
NO RUSH TO DIVE INTO VRI
Mid-Atlantic farmers with an adequate water supply for irrigation will find that variable-rate irrigation (VRI) probably doesn't pencil out, University of Delaware irrigation engineer James Adkins suggests.
In 2012, Adkins retrofitted a pivot system at the Warrington Irrigation Research Farm for zone control VRI. The system is used for crop research. Adkins says it costs $5,000 per span to retrofit a pivot with zone control VRI, or $20,000 for the four-span system at Warrington Farm. The Delaware irrigation specialist makes his irrigation decisions based on information from sensors in each field.
"At today's corn prices for farmers, VRI doesn't pencil out for most fields in our region," Adkins says.
Joel Schneekloth is also skeptical about the return on investment from VRI in the High Plains. Schneekloth is a regional water resource specialist for Colorado State University.
"As a rule, our soils in the High Plains aren't as variable as those in some areas," he says. "The bottom line to ask yourself is if you'll make a reasonable rate of return from a significant investment."
(BAS)
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