Time to put your potatoes to bed

Those long, arrow-straight rows of carefully hilled potato plants are one of the key features of any potato production region — but in a few years they might be a thing of the past, says a soil scientist from USDA.

David Tarkalson, a member of the USDA’s Agricultural Research Service based in Kimberly, Idaho, thinks bed planting shows a lot of promise.

The system eschews the traditional hilled rows in favour of a raised bed that contains either five or seven rows, depending on the equipment used to plant them and cover the seed.

“They’re not completely flat — there’s some microtopography going on in them,” Tarkalson told the Manitoba Potato Production Days meeting last winter. “There is some hilling to provide closure over the seed, but they’re not as pronounced as a conventional hilled system.”

Pioneering a new way of planting and managing potatoes isn’t something to take lightly, he said, but rather is likely to become necessary as the available water resources become more constrained.

“We’re looking at a future with less available water,” he said. “We have some producers with limited water for various reasons, and they’re concerned about the future if there’s not enough water, so the question is how to grow with less water, how to conserve water. We’re not looking to increase production, but to save water.”

For example, some typical water numbers for Idaho show that farmers can expect three to six inches of precipitation in an average growing year. Frequently key periods of the growing season — July, August and September — are completely rain free. A thriving potato crop needs 30 inches or so to see it through.

“We’re very dry,” he said. “There’s no problem with too much water in our profile, we’re trying to preserve it, and beds hold a lot more water than our conventional system.”

Besides, the conventional systems grew out of necessities way back in the day which aren’t likely to apply today, Tarkalson said.

“Our hill configuration really is a practice from tradition,” he said. “They needed a place for the horse to walk, on 36-inch centres. In wet areas, it’s a great way to get water away from roots. In Idaho it worked well because water was applied in the furrow, which is a great place to run water.”

Today horses are a thing of the past and almost all the irrigation water in the state is applied with high-intensity sprayer systems.

“We’re no longer constrained to stay with the conventional system,” he said.

Benefits

There’s plenty of research pointing to the merits of this new approach, Tarkalson said.

Research has shown that of the two options — five-row beds and seven-row beds — the five-row strategy may work better, when planted with a slightly higher population of around 10 per cent over the usual density.

“We grew common cultivars and measured water use and total yield,” he said. “Irrigation was standard applications, as determined by the growers.”

On average these five-row bed treatments yielded 25 cwt an acre higher, and used 2.5 less inches of water to do so, a combination that made them much more efficient. Tarkalson said the beds appear to have higher yields because they use nutrients more efficiently and make more efficient use of available sunlight by reducing the open soil in each field.

He did, however, caution that results varied by variety planted, and that the most inconsistent variety appeared to be the industry-standard french fry potato, Russet Burbank. It could yield better and use less water — or it could deliver very disappointing results.

“If you’re growing Russet Burbank, we don’t know enough yet to tell you what’s going to happen,” he said. “Other varieties we can predict, but we can’t say that for Russet Burbank yet.”

Another issue is tuber size — the average tuber size is smaller in the bed. That’s likely related to grower practices in the field, and experimenting with row spacings may enable better control over tuber size. Tarkalson also noted there may be opportunities to target specific markets based on tuber size, such as fingerling potatoes or seed potatoes.

However, many varieties planted in beds did a more efficient job of capturing the available sunlight for plant photosynthesis. For example, the five-row bed treatment intercepted 38 per cent more sunlight than the conventional treatment.

“It did a better job of turning sunlight into carbohydrate energy,” Tarkalson said.

Again, however, the lone outlier was the Russet Burbank, which showed little to no response, which seemed to capture as much sunlight in rows as beds, while the up-and-coming varieties Norkotah and Ranger Russet did intercept more light over the course of the season.

“Something in the growth pattern of Russet Burbank is negating this effect,” Tarkalson said. “At the end of the season there was not a whole lot of difference.”w

Growers who have experimented with the technique in Idaho are pleased with it, especially in areas that are water challenged. Tarkalson told the story of one large operation in eastern Idaho who found they were saving between 3.5 and four inches of water a season, with identical yields.

“Over the last five years they’ve gone from doing this on 40 acres to 100, then 200, 400 and they’re up to 800 this year,” Tarkalson said. “They’re very pleased with it.”

Will the experiment translate to Manitoba? That all depends on whether growers think the need to save water is important enough, Tarkalson said, and whether they’re typically trying to conserve water or get rid of it. Sandy land might be suited, but heavier clays wouldn’t be.

“If you’re trying to get rid of water, shy away from this,” Tarkalson said. “And if you are going to try it, I’d encourage you to follow the pattern we’ve seen — start small, make your big mistakes on a small amount of ground, fine tune it, and then, if it works, expand it.”

About the author

Editor

Gord Gilmour

Gord Gilmour is Editor of the Manitoba Co-operator.

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