A french fry that spills out of the box has environmental consequences. (CBC)

Long french fries, the kind favoured by fast food restaurants, are contributing to excess nitrates in P.E.I.'s groundwater, says a new report.

The report on nitrates in groundwater contains 30 recommendations to government to help reduce growing concentrations of nitrates in P.E.I. groundwater. One of those recommendations — to change the type of potatoes grown — has far-reaching consequences.

"Efforts must be made to convince makers and consumers of potato products ... that the use of more nitrogen efficient varieties ... would be of significant environmental benefit," reads the report released Tuesday.

From the farmer's perspective, a different variety of potato could go in the ground in the spring, but much of the Island's potato industry is built on the Russet Burbank potato, a century-old variety that is the foundation of the french fry industry.

White-fleshed and roughly the size of a brick, the Russet Burbank makes what is considered to be the perfect french fry, because if you want a long fry, you need a long potato. The late harvest of potatoes leaves fields bare through the late autumn and into early spring. (CBC)

The trouble is, it takes a long time to grow a long potato, about 120 days on P.E.I. That means harvest time comes in late October, too late for a cover crop such as winter rye to get started. Fields lie bare through the late autumn, winter and early spring, and excess nitrogen from fertilizers washes down into the soil.

"[Winter rye] is strong growing and it will cover," potato grower Terry Curley told CBC News Thursday. "It stops a lot of the erosion."

If the potatoes came out of the ground earlier, a cover crop would trap excess nitrogen, and help prevent soil erosion at the same time.

It comes down to timing. Harvest is usually too late for Russet Burbank growers to plant a cover crop.

Changing what people want in a fry will likely be difficult. Even a casual survey of fast food customers in Charlottetown reveals that they understand the appeal of the long fry.

"I'd eat short or long; they're both good," Ralph Sanderson said. "But the long one fills the container up better."

With P.E.I. french fry makers supplying international fast food giants, implementing the recommendation on potato types from the nitrates commission could prove difficult.