Farmers should carefully consider cost of irrigation systems, researcher finds

Most years on P.E.I. the gains a potato farmer would make from irrigation would not be worth the cost of installing and operating the system, a new research paper suggests.

The study, with Charlottetown-based Agriculture Canada research scientist Yefang Jiang as the lead author, was recently published in the journal Agricultural Water Management. It looked at rainfall during the growing season and compared it to yields going back to 2000.

The researchers found in 90 per cent of seasons they measured, irrigation was too expensive to be worthwhile.

"That would bring no change to yield to such a level that can offset the cost of your investment in irrigation," said Jiang.

"That's what we found."

The researchers looked at rainfall, along with other factors, and compared it to yields. They determined water is the crucial factor for optimum yield, accounting for 88 per cent of yield variation in the years studied. They also found P.E.I. comes up a little short on optimum rainfall, on average about 80 millimetres short for the June to September growing season.

And while farmers could increase yields in those years that are a little bit dry, it would not be by so much that it would offset the installation and operating cost of the irrigation, said Jiang.

The paper includes estimates of irrigation costs and compares them to projected gains from increased yields. It found in a typical year farmers could earn another $754 per hectare with irrigation. Irrigation, including the development of a water source such as a high-capacity well, would cost them between $1,335 and $2,684 per hectare, depending on the size of the field.

In a very dry year the system would pay for itself, adding $3,040 per hectare to yields.

Jiang noted the paper's authors used irrigation system costs from Maine, and that those could be different on P.E.I.

Irrigation controversial

Since 2001, P.E.I. farmers have not had a choice about digging a high-capacity well to feed a supplemental irrigation system, because a moratorium on the wells for agricultural uses has been in place.

Effective in September, that moratorium has been lifted.

The change comes with the province's new Water Act, and follows intense lobbying by the P.E.I. Potato Board.

Board general manager Greg Donald cautions that while the new study contains important information, it can't be applied to every individual farm on P.E.I.

The study used rainfall measurements from the Agriculture Canada research station at Harrington. Donald said it is important to remember that rainfall on the Island, even though the province is small, can vary a lot.

Donald used the example of 2020, which was dry all over, but particularly in the central area.

"We saw some potato farms with yields down as much as 35 per cent," he said.

"In the western and eastern end of the Island, it was still stress conditions, from moisture, but it didn't have the impact on the crops as the central area."

Calculating the value of an irrigation system is not necessarily as simple as calculating the cost of a bad year, said Donald. Some farmers have supply deals with large companies, and if a year or two goes by where their supply is short they risk losing those customers. That can put the continued existence of the farm in jeopardy.

"It's somewhat of a pretty expensive insurance policy for farms on those really bad years," said Donald.

The P.E.I. Potato Board has always advocated for responsible use of the water resource, he said.

"They'll be limited situations where it will be a tool that'll be used, but in some areas of P.E.I. it'll be one that'll be more necessary," said Donald.

Too much rain

The researchers found that too much rain can also reduce yields.

Farmers might want to consider tile drainage, which allows excess water to run off, said Jiang. This could also bring benefits in the planting and harvesting seasons. A field with tile drainage may dry out more quickly in the spring for earlier planting.

"You have a longer growing season [when] you plant earlier, and then you can get better yield," he said.

"In 2018, in the fall it was so wet, and then farmers couldn't harvest a lot of potatoes, and that's a loss as well. But if you have tile draining the soil you may be able to harvest a little bit more."

The paper did not include a costing for tile drainage, and Jiang noted slopes in some P.E.I. potato fields are too steep for tile drainage.

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