Now it’s variable rate irrigation

Variable rate irrigation is just getting started, but it could be the future of a more efficient way to use water and manage high-value irrigation crops

Variable rate technology is already enabling more efficient use of fertilizer. “Variable rate irrigation could be as big a boost to water use efficiency.”

That’s the opinion of Dana Williams-Freeman, manager of Oliver Irrigation in Lethbridge.

“It lets us avoid over-application of water,” he says. “That means better crops, and more efficient use of water, maybe 30 per cent savings, just by not over-watering any part of the field.”

Some farmers have been dividing their fields into production zones and adjusting fertilizer and sometimes seeding rates to match each zone’s yield potential. Many farmers wonder if higher margins will justify the cost and effort of zone management.

Under irrigation, fields tend to look more even than dryland crops, but a pivot sometimes has to run across a slough or some other obstacle. Different soil textures may affect water needs in some parts of a field.

Digital control panels and GPS units on the end of pivot arms have allowed farmers to alter the amount of water a pivot puts on a particular segment of a field without having to be there at the right time to change the settings. Some use this feature to have the pivot run dry over a part of its circle, or apply different amounts of water on the crops seeded each side of a split circle by changing its speed.

A few people have developed computer programs to achieve more complex watering patterns, but they’ve been limited to changing the amount of water on a segment of the pivot circle.

New technology

The variable rate irrigation system sold by Valley Irrigation, for which Oliver is the dealer, allows you to load a field map into the control panel and apply the ideal amount of water to each part of the field. The system has control boxes mounted on the support towers. Each box controls four to 10 valves, each one controlling water flow to a sprinkler. The control box on the tower sends signals to the valves to cycle them on and off to adjust the volume of water applied.

The Valley variable rate irrigation system can adjust a quarter-section pivot to apply water for up to 145 zones. Programming the system is part of pivot setup, not something you’d need to change when you’re busy with field work.

“We work out all the details as we configure the system,” says Williams-Freeman.

Williams-Freeman sees better crop quality as the main benefit from the precise control of moisture levels. The big gains could be in high value crops like potatoes, but also to help avoid disease conditions in heavy crops in low areas.

Lindsay Irrigation has developed a variable rate irrigation system that can be used on any pivot to control every sprinkler electronically and can be used with any manufacturer’s control panel. It’s combined with an RTK GPS system that allows the system to change the output of any sprinkler with each quarter-inch of pivot travel.

“We can avoid watering a roadway, a pond, a saline area or any other obstacle anywhere in the field,” says David Gross, of New-Way Irrigation in Lethbridge, the dealer for Lindsay Irrigation. “This system can use any prescription map.

“Perhaps the biggest advantage I see is that a farmer can avoid applying water to an area, so they might be able to move some acres to another field — although that would depend on the Irrigation District.”

Not irrigating non-productive areas would be good for the environment as well, because run-offwould be reduced.

Williams-Freeman sees huge potential for these systems as the technology improvise and farmers and irrigation companies learn to use them effectively.

“The technology is still in its infancy. We need to establish a pool of knowledge to help us judge the best way to do things.”

This article originally appeared in the Fall 2011 issue of “Farming Smarter,” a magazine published by the Southern Applied Research Association based in Lethbridge, Alta. It is reprinted with permission. †

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