OUTLOOK, Sask. – Bill King has a routine on his market garden near Outlook: every day he hooks up a garden hose and washes the metal cylindrical filters inside his irrigation pumps.
This low-tech but effective method keeps the water flowing from irrigation canals to his fruit and vegetable fields while preventing emitters and lines from clogging with minerals and debris.
He flushes the entire system with bleach once a year, leaving it to sit in the lines overnight before washing it out the next day.
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“I open it up and if it smells like chlorine, I know it made it that far,” he said.
Ted Van der Gulik, a senior engineer with the British Columbia agriculture ministry of agriculture and lands, said King had the right idea.
During a two-day workshop in Outlook last month on trickle irrigation, Van der Gulik stressed the importance of good irrigation system filtration and maintenance.
Picking the right filter and matching it to the irrigation system are keys to success, he added.
“If it will fail, it will fail because of poor filtration.”
He said a screen can handle sediments while a 2.5 centimetre-thick disk filter can handle greater amounts. A metre-deep sand filter tank can hold more material and deal with higher levels of organics.
“The bigger the holding capacity the less frequently you have to clean them,” Van der Gulik said.
Filters should be matched to the emitter size.
A larger opening allows more material to pass through and lessens the need for as fine a filtration system. A 200 mesh screen works well with an emitter opening that is 1,000 microns wide
Van der Gulik said the lines must be flushed at least twice a year with chlorine to prevent algae growth and then flushed again to remove the chlorine.
He recommended injecting concentrations of up to 40 millilitres of chlorine per litre of water into the lines for four hours at a time.
“If 40 ppm (parts per million) is not doing a good job, there’s no point going any higher.”
Van der Gulik advised flushing at the start and end of the growing year and possibly once during the season.
“For five, 10, 15 years of line, you’ve got to maintain the product.”
Flushing is probably not necessary for drip tape lines set down for a year’s use, he added.
Producers can set automatic timers to periodically flush lines and install sensors to detect clogged filters and start an automatic system that backwashes or flushes water through the lines to clear them out.
“It costs you money but saves you a lot of labour,” he said, estimating such devices cost $3,000 to $5,000.
Water quality is a major factor in trickle irrigation, so Van der Gulik recommended that producers start with a complete study of sediments, minerals and organics in the farm’s water source.
“If it’s causing you problems, it’s something you shouldn’t use,” he said.”If it’s acceptable, figure out the treatments you want to do.”
He said such water quality and salinity problems are more common in provinces such as Saskatchewan where ground water is used for irrigation, rather than in provinces such as British Columbia, which uses water from mountain runoff.
Saskatchewan Agriculture annually evaluates soil and water capability on 7,000 to 12,000 acres of land slated for irrigation, said Kelly Farden, a provincial irrigation agrologist.
The provincial irrigation act requires such studies for producers wanting to obtain a licence to irrigate 10 or more acres. The fee is $1,365 for the first quarter and $1,155 for each additional quarter.
Farden said demand is strong this year because of improved commodity prices. Drought years also see more requests for evaluations, he added.
“Economically it makes more sense,” he said. “You want to make sure the soil is suitable for development. If not, you might not get the returns you need to make it pay for itself.”
Irrigating a field with too much salinity can degrade the soil, while irrigation can also bring more salt to the surface from greater depths.
“We want to be sure irrigation is done in a sustainable way,” Farden said.
