Prepping Your Potato Seed for Spring


What you need to keep in mind to get your potato seed ready for planting this spring.


Khalil Al-Mughrabi
Khalil Al-Mughrabi, provincial potato pathologist with the New Brunswick Department of Agriculture, Aquaculture and Fisheries
Ryan Barrett
Ryan Barrett, research and agronomy specialist with the Prince Edward Island Potato Board

Editor’s note: This interview has been edited for length and clarity. 

Spud Smart (SS): Why are potato seed treatments important?

Khalil Al-Mughrabi (KA): Potato seed treatment is important. One of the most important pest management practices that growers can follow or should follow is planting disease free certified seed potatoes. So, if high quality seed stock is planted and properly healed after cutting seed piece decay can be minimal, providing that conditions at planting and consequently after planting, allow for rapid emergence and growth.

Late blight
Late blight infected seed potatoes. Photo: Khalil Al-Mughrabi

So, seed piece treatment can be a valuable insurance in the event conditions deteriorate after planting. In Canada there are several products that are registered for seed treatments, much of which are targeting fusarium dry rot, and some target rhizoctonia and silver scurf… While seedborne late blight has three products — Reason, Revus and Vibrance Ultra.

SS: What is physiological age and why does it matter when it comes to seed potatoes?

Ryan Barrett (RB): Physiological age seed is largely influenced by the variety — the end use is going to be a big part of this. A huge factor in the physiological age of seed is the growing conditions of the year before, like was the year before hot and dry? If it was your seeds probably will be more physiologically aged than if it was an ideal growing season, or if you had all your seed under irrigation.

The storage temperature that you’re keeping your seed at is important — at about 4 C we’re not adding age on to the seed, but above that we are. Importantly, we really can’t turn the clock backwards. So, as we add age to seed, we can’t really reverse that.

And why this is important is that as seed gets older, it generally breaks apical dominance, and we usually have more tubers of smaller size. As we have younger seed, we usually have fewer tubers of larger size. If you’re going Russet Burbank, or other varieties that normally set a lot of tubers, and you want to make sure you don’t get small ones in your resulting commercial crop, you may want to keep that seed younger. If you’re growing a variety that generally has fewer tubers plant, like Dakota Russet, then there can be advantages to adding age to your seed.

SS: How does seed size impact row spacing when planting potatoes?

RB: In our trials, we have seen that the small whole seed and the large whole seed in general had the same or better yield than the cut seed with slightly fewer defects, slightly more smalls and less per cent over 10-ounce. The larger whole seed pieces, those two and a half to four-ounce seed pieces, they did have a higher dollars per acre in terms of result and value.

P.E.I. potato field
A potato field on Prince Edward Island being planted. Photo: Ryan Barrett

What becomes clear is that when you’re comparing cut seed against whole seed, one thing that we really need to do is dial in exactly what our seed spacing is. The bigger the seed piece, either whole or cut, the more that we’re going to have to increase the seed spacing. Likewise, the smaller the seed we’ll have to tighten that spacing up a little bit.

SS: What should you keep in mind regarding size when cutting seed tubers?

RB: This year in a lot of parts of Canada and North America, seed supply is tight. So, there can be pressure on the grower side to cut seeds smaller because they want to make their seed go further because they just don’t have that much seed around. But we’ve seen in a lot of trials over a lot of years that smaller seed pieces with more cut edges and smaller overall size do have a lower yield potential, a higher risk of non-emergence, and they generally don’t pay for themselves. So, what is the sweet spot for cutting seed size?

Larger seed piece size is generally associated with better yield. In general, cut seed pieces under one and a half ounce they struggle to produce a viable plant or if they do, they’re more at risk of disease. Keeping your average seed size to 2.3 to 2.5 ounces is usually about the sweet spot for most varieties. Depending on the variety you may have to adjust that slightly.

SS: What should growers keep in mind when it comes to potato seed handling?

RB: One of the main priorities is reducing drop height. Try and keep that drop height to less than six inches, and ideally as low as possible the better. Monitoring that bin piler or the conveyors and keeping it level with where the seed is dropping will minimize that drop height to less than an inch. Hopefully, that’s not going to put any bruise on that cut seed as it’s moving through the cutting and loading process, which is terrific.

Drop Height
Seed potatoes being loaded at a reduced drop height to reduce injuries to seed. Photo: Ryan Barrett

Set cutter disinfection is a big story that we’ve talked about in recent years, particularly as we see some more aggressive strains of blackleg around. Growers face a variety of seed-borne disease issues, such as soft rot, BRR and other bacterial diseases, and fungal diseases like Fusarium. So, seed cutter disinfection is a very important.

When it comes to set cutter maintenance and calibration, make sure your rollers are on the right sizes. Adjust those flow volumes to ensure that you’ve got even cutting, you don’t have potatoes bunching up and getting on top of each other, that you’ve got bruising from bouncing around and maybe not being cut in the right place. Keep the knives sharp to avoid jagged edges on your cut surfaces. Check that horizontal knife for the ones that are getting cut in half on the top, ensuring that it is cutting those tubers evenly. Finally, open up that chip eliminator to discard those pieces less than 1.5 ounces. Remember those small seed pieces you might grow a plant, but they’re not going to they’re not going to pay for themselves. It’s important to frequently take samples of your seed profile during cutting to ensure that you’re meeting your targeted average seed piece size while keeping as tight of a distribution on size as possible.

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Ashley Robinson was raised on a mixed cattle and grain farm in southwestern Manitoba. She attended the University of Regina where she studied journalism. Following university, she has spent the better part of the past decade writing about agriculture in publications across Canada and internationally. Robinson’s agriculture writing has covered topics from rural issues to commodity markets. Since joining Seed World Group her work has focused on covering all aspects of the Canadian potato industry from planting to farm management, and agriculture in Alberta focusing on how the seed industry connects to farmer’s daily lives.