Drier conditions prompt new look at irrigation

Drier conditions prompt new look at irrigation

Different crops have different peak water needs so supplying available water at the most vital time can conserve water

Several southern Alberta irrigation districts put restrictions on water use last spring when dry conditions raised the spectre of insufficient supply to meet crop needs.

Those restrictions were lifted when precipitation improved but they highlighted the wisdom of planning for similar limits should they occur in the future.

“As we get potential climate change, perhaps we’re going to get drier seasons, a little bit more pressure from other water users on what happens with that water,” said Alberta Agriculture research scientist Michele Konschuh.

“There’s always an incentive to become more efficient with the water that we’re provided with.”

Different crops have different peak water needs so supplying available water at the most vital time in the growth cycle can conserve water, she told those at the Alberta Irrigation Districts Association water conference.

Adequate moisture for an alfalfa crop, for example, is most vital at the establishment stage. Barley and wheat need it most at flowering and canola requires optimum moisture particularly at flowering and pod fill.

“Typically that crop time frame where you need to be really paying attention to water is during reproductive growth stage,” said Konschuh. “There’s some key stages of development with each crop and it’s important that you pay attention to those stages if you have to restrict water allocation.”

Another irrigation management approach, if water is restricted, is to not irrigate all acres. Irrigating all crops less that adequately can cost more than giving adequate water to fewer acres, she said.

“Some crops are so expensive to grow that deficit irrigation is never going to pencil out. So when both your yield and quality are affected by irrigation management, and both yield and quality affect the value of that crop considerably, your best option will always be to irrigate those crops fully and then reduce either the acreage of those crops or reduce your allocation on other less sensitive crops so that you can irrigate your most expensive crops best.”

Crop rotation can also assist in spreading out irrigation demand because their needs can extend beyond the critical demand period of most other crops.

“Sometimes you can still honour a rotation but you can choose crops that are a little bit more tolerant of restricted water allocation.”

There are other management strategies to make best use of available irrigation water. Reduced tillage, residue management and altering seeding rates are among them, as is good weed control.

“Weeds are particularly well adapted to limited water supplies and they will outcompete your crop. So you never want to let weeds grow in your field but in a year when your water is limited, it’s even more important that you keep a handle on your weed control. And stressed crops … are going to be a little more susceptible to diseases and pests,” Konschuh said.

Optimum use of irrigation also depends on fertilizer. Applications of fertilizer without supplying sufficient irrigation is simply a waste, she said.

“The plant can’t use it if there isn’t enough water there to make use of it. You want to make sure that the fertilization is paired well with your intended water use.”

System maintenance also conserves water. Replacement of worn sprinklers, good drains and gaskets and repair of leaks will contribute to efficiency. Water restrictions can also be the impetus to upgrade older systems.

“If it’s feasible, upgrading from a wheel move to a pivot irrigation can increase your water use efficiency by up to 15 percent and right now the government does have a program called the Irrigation Efficiency Program that will assist producers with a portion of those costs,” Konschuh said.

As of early February, mountain snow pack that feeds river systems and reservoirs is average to above and there are no indications that irrigation districts face abnormally dry conditions in the coming season.

Additional irrigation information is available here.

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