Variable rate irrigation makes debut More efficient use of water » by Helen McMenamin
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ariable rate irrigation could be as big a boost to water use efficiency as the switch to low pressure pivots from our old high impact sprinklers that used 60 p.s.i. to shoot water up into the air.” 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.” Williams-Freeman foresees situations where this technology would save enough water for a farmer to have a good case for asking to irrigate more land. That will take water-metreing at the farm, but that is becoming feasible with pipelines and accurate electronic metre systems. The amount of water each part of a field can use is as variable as fertilizer needs or the ideal seeding rate. Now you can set up a pivot to apply just the amount of water each part of the field needs.
Some pivot systems allow you to load a field map into the control panel and apply the ideal amount of water to each part of the 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. Most people used 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. A few people have developed their own 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. Now, you can irrigate a field to match soil type and topography, no matter how the various zones are aligned compared to the pivot arm. Most of a field might be sandy, but with low-lying soils that need less water. The program for a basin might gradually decrease water application on the slopes, going down to 50 per cent on the bottom. Continues on next page »
Credit: C. Lacombe
Farming Smarter / Fall 2011
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