EDMONTON – Potato production can be a lucrative business for market gardeners and a decent source of supplemental income for farm families, says Patricia McAllister, an Alberta Agriculture seed potato specialist who provided hints and tips to help market garden operations during the Alberta Horticulture Congress in Edmonton last month.
She said Statistics Canada data shows that Alberta has about 500 commercial potato growers, producing more than 50,000 acres of potatoes, mostly for processing plants in the southern part of the province.
“We’re also between 12,000 and 13,000 acres of potatoes for seed and close to 5,000 acres for the fresh market.”
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McAllister said Alberta seed potatoes start in a tissue culture lab and proceed to a greenhouse-protected environment before entering the field. That level is considered nuclear and is followed by the first field generation, called pre-elite. Successive field generations, elite 1 to elite 4, are followed by foundation and certified.
“We don’t include foundation and certified because we don’t grow them. Alberta is unique in Canada, in that we only have four field generations of seed before we’re putting them out for commercial production,” she said.
“That’s why we have so many different varieties available and why Alberta is renowned as being a producer of high quality seed. We have the greenhouse environment, so we can be sure we’re moving and flushing potatoes through the system, to prevent the buildup of disease.”
Initial production starts as a tissue cultured plant. The greenhouses that grow them must meet specific Canadian Food Inspection Agency requirements, including screened intake and exhaust fans to keep out insects and ensure cleanliness. The little potatoes produced in the greenhouses are worth 60 to 75 cents apiece.
Sanitation on a seed potato farm is legislated by CFIA. Disinfecting planters, harvesters, storage equipment and containers is critical.
Diseases such as late blight can be devastating, not only for potatoes but also tomatoes. McAllister said Alberta has been free of late blight for four years, which means it’s a bad idea to bring in seed from other areas, especially those with late blight problems.
“You could be planting inoculum that could end up destroying your potatoes and tomatoes.”
Planting
Whole seed is a benefit to planting in cold soil. McAllister said it’s not a good idea to cut a seed piece and throw the fresh cut in the ground at 4 C. Whole seed is much more resilient.
“Seed piece treatments for disease control, especially if you’re cutting, can be your best friend,” she said.
Hormone applications for seed set and size control are being tested. McAllister said work with gibberellic acid is under way in an attempt to increase tuber set.
“We’re in the process of trying to get a variety registered for that use, so you can treat your whole seed and get all the eyes on it to sprout,” she said.
“Then you end up with a higher tuber set and smaller tuber size profile.”
She said the process works well for seed producers, but may also work for producers trying to market a smaller-sized product.
“A uniform seed piece size means uniform crop in the field. It also makes planting easier. If you have some that can be planted whole and some that need to be cut, plant that whole stuff together. It’s going to behave differently than what you’ve cut. If you can sort your seed by size and cuts, you’ll have a much more uniform crop.”
Seed piece spacing depends on the variety and end use. McAllister said some seed growers produce specific potato varieties for Mexico that have to be 35 to 55 millimetres in diameter.
“They’re planting that 4.5 to 6.5 inches (11.5 to 16.5 centimetres) apart. If you’re doing dryland production of Russet Burbanks for storage, you might want those 12 inches (30.5 cm) apart. In Eastern Canada, they put Burbanks as far as 18 inches (46 cm) apart. Market and what your desired size profile are have a lot to do with how you plant that crop.”
Depth
McAllister recommended planting shallowly if planting early into cold soil.
“You have to get that out of the ground before disease starts taking off your sprouts. In warm conditions, you can plant deeper and still get a successful crop.”
Sweating is another problem.
“If your potato is cold and your soil is warm – you take it right out of cold storage and plant it – you’ll get condensation just like on your water glass. You’ll get all kinds of disease issues around that seed piece. That free water will lead to seed piece decay.”
Hilling
McAllister said a proper hill is critical for optimum potato production.
“Your hill is everything. A potato is an underground stem. You have to put leaf (buds) under the ground, to turn into stolons, in order to get tuber production. If you don’t hill you are not maximizing your productivity. The more you can hill, the more potential you have.”
The hill is critical for tuber set and also helps prevent greening. Green potatoes are lost money.
“We recommend a flat-topped hill. A pointed hill means you’re losing yield potential on either side. To maximize your production area, you want a flat hill with almost square shoulders,” she said.
“We actually hill our plots before they come up. You don’t want to do any root pruning. If you do that, you’re losing yield. The less disturbance you do, the better. If you get a really big hill on them, you don’t have to go back and touch them. Ideally, you only have to do it once.”
Scab
Regular watering, especially during tuber initiation and early development, should reduce common scab, McAllister said. With long periods of drought, the scab organism will attach to the potato as a source of moisture, which is where the problem originates.
“The other scab is a fungus and it needs water to grow, especially when tuber size is in the nickel to quarter range. But that’s powdery scab and most times you’re dealing with common scab.”
Harvest
McAllister said harvest is a big, messy job with lots of potential to cut tubers. Every wound made in a tuber can potentially lead to a disease.
“Whether you’re digging with a shovel or a digger, when you ding, cut, skin or scrape them, that soil has lots of disease in it. You’re rubbing the disease right in and you have to be careful how you manage it.”
Suberization, which is a wound-healing process no different than a human body forming a scab, is an important post-harvest treatment.
“You need 12 to 15 C at 90 to 95 percent relative humidity, for 10 days to two weeks,” she said.
“If you’re taking those potatoes out of the ground at 5 C, you’ve got to warm them up in order to make sure the skin heals properly. If you try to keep them cold and dry during the suberization process, you will not get successful wound healing. Likely something will infect your potato before it’s done.”
Temperature, humidity and air movement increase storability.
“A potato is alive. It needs oxygen and needs to move the carbon dioxide away and it needs to make sure there’s no buildup from forklift exhaust and other things that can result in premature sprouting.”
McAllister said she doesn’t think potatoes should be planted in Alberta before the long weekend in May. Plants can take five weeks to come up, or 14 days, depending on soil conditions.
“In my own research trials, I’ve planted the first week in May and the third week in May and my end result is always the same. They don’t like cold, wet soil and you’re losing yield potential.”
One option is to perform a function called green sprouting, where potatoes are allowed to sprout before seeding.
“If you can take advantage of greenhouse space you may have from another part of your operation, get them warm, ready to grow and wait until the soil is ready, you’ll definitely see an advantage. I’ve tuber unit planted potatoes that had leaves on them, and I’m telling you, they fly out of the ground. Green sprouting, especially for early market, is a huge advantage.”
Soil temperature should be above 8 C. Green sprouted seed at 15 C means much faster emergence and a healthier crop.
