AgronomyDamage Control

Damage Control


[deck]Four growers from across Canada discuss how they minimize bruise damage on the farm.[/deck]

spud_summer2012_25 Gary Linkletter is chairman of the Prince Edward Island Potato Board and a partner of Linkletter Farms Ltd. He farms 1,500 acres of fresh-pack potatoes near Summerside, P.E.I.
spud_summer2012_26 Mark VanOostrum is the field manager and quality supervisor for W.D. Potato Ltd. in Beeton, Ont. He oversees 50 growers and 15,000 acres of chip-stock potato production in Ontario, Quebec, Nova Scotia and Prince Edward Island.
spud_summer2012_27 Andrew Kazakoff is a member of the Saskatchewan Seed Potato Growers’ Association and a partner of Assiniboine Valley Seed Potatoes Ltd. He farms 140 acres of seed potatoes near Kamsack, Sask.
spud_summer2012_28 Tim Guichon is a member of BCfresh and a partner of Felix Farms Ltd. He produces 900 acres of new and table potatoes in Delta and Abbotsford, B.C.

Spud Smart: What practices do you employ at harvest to minimize or prevent bruising and wounding?

GL: The most profitable thing we do on the farm is we employ two people to do bruise testing for each harvester and that is their entire job. We try to take 10 potatoes off of every load that comes in for bruise testing. Those loads come in every 10 minutes. We get a very accurate picture of bruising—we like to keep it under three per cent. The testers can catch me on my cell phone or radio in the field if there is a problem, and I’ll tell the operator. The operator will respond, and if he needs any help I can go over the machine with him.

I also check the depth of the harvesters, windrowers and so on. If someone starts getting up there [in terms of bruising], for example, if the shear height’s a little too high, the bruise testing will usually show that before we have a problem. If bruising starts to creep up it’s important to catch it before it gets really bad; however, what you do about it can vary.

MV: We pay particular attention to our pulp temperatures. During harvest this is crucial for bruise reduction. We’ve tweaked the window here—we try to prevent harvesting below 47 degrees Fahrenheit, and we’ve tried to dig as much of the crop as possible over 52 degrees Fahrenheit.

We also spend time training, empowering and educating employees about the importance of bruising, and to watch for it every minute of the day. Sometimes the best operator can run the oldest, roughest equipment and produce chipping potatoes that look like they’ve been handled like eggs. We’ve also seen a rough operator use the newest technology and equipment and produce potatoes that are very bruised.
We’ve modified equipment—lots of padding and chutes to reduce drops. In growing areas where we have many clods and rocks, we focus on getting them out of the line as quickly as possible. We have an extensive bruise-testing program. We use a hotbox system where we put samples in a hot room at 100 degrees Fahrenheit for 24 hours. That sample tells us what the potatoes will look like later in storage. We do that constantly through the harvest season for all of our supply.

AK: It starts right from the field—you have to be careful when you’re handling potatoes because if you bruise them in the field, no matter what you do after that it’s not going to help. For example, don’t keep the boom too high above the potatoes.

Drop the potatoes as little as possible. A rule of thumb is to reduce drops to a foot or less. Even putting them into wooden boxes I use a cushion of some sort to deflect the potatoes, otherwise they will be rotten in the spring, even with a little drop.

We run the machinery at full capacity as much as we can. We try to keep some dirt in the conveyor, but depending upon conditions, sometimes we have too much dirt and we have clumps, and in other places, with variable soils, the sand falls right through.

TG: For our farm, it starts right at planting with how we prepare the field. Our early ground is a sandy loam soil and we finish off in the heaviest clay you’ve ever seen. There’s a huge difference in what we do with the sandy loam soil when compared with the heavy clay soil.

From seed cutters right through to our end-of-line packing house—we’re looking at all of it. We also wash samples and check for problems with the harvester, piler and trucks every day, and we try not to harvest when it’s too hot and dry or cold and wet.

However, the biggest thing is personnel training and refreshing that training every year. Management of your harvester operators is absolutely critical. The people who run our harvesters have been with us for years. They are conscientious and they grade the potatoes in the winter, so they see what they dug up in the fall.

SS: In your experience, what has been one of the biggest sources of potato bruising at harvest time, and what have you done to minimize or prevent this damage?

GL: The biggest issue is chain speed and the amount of clay you are carrying. When you’ve got lots of clay and it has been wet, you run your chains a little faster and you try to shake things out. Sometimes the soil has dried, but you’re still operating as if it was wet. All of a sudden your chain speed is going too fast because the clay is dropping through and the potatoes are bouncing on the chains. You have to speed up so more clay fills the chains—you can’t let the potatoes bounce, that’s the bottom line.

How full are the primaries and are the potatoes bouncing? These are the first things I look for when I walk beside the harvesters and windrowers. If you don’t have enough clay in the primaries, there will not be enough left for the secondaries to work with.

MV: Our number one issue to manage is pulp temperature. Under 50 degrees Fahrenheit we see an exponential increase in the amount and severity of bruising. Once you get into the 47 degrees Fahrenheit range you are definitely bruising a lot of potatoes, so the chip quality suffers and loads may come back due to high defects. We manage pulp temperature right from the start [of the season] to the end. For example, we try to plant early and efficiently, we also look at nitrogen management to ensure we’re not putting on too much nitrogen and pushing the crop later into the fall. We watch our field selection; for example, we adjust the variety we put into a heavy field so that it has a shorter growing season as opposed to putting a long-season variety into a late-planted field. That also leads into top-kill timing—we’re getting onto the fields at a decent time in August so that we can start our harvest as early as we can.

We’ve invested in equipment so we put away more loads per day when conditions are ideal, such as larger harvesters, evenflow hoppers and telescopic elevators. We also do more cleaning in the field so that we can unload trucks faster at the storage.

AK: Rough handling is the biggest source of damage. It might not look like you’re damaging the potatoes at harvest, but in the spring they will be damaged. I am constantly careful about how much and how far we drop the potatoes.

TG: Equipment set-up and the operation of that equipment are key. It’s important to go over the equipment—most of that involves the initial set up, and then personnel training to minimize bruising.

SS: Have you grown any varieties new to you in the past five years? Were harvest practices adjusted considering harvest management recommendations particular to that variety?

GL: By checking every load you can easily identify if the variety is tender. Some varieties are more tender than others and some, like Burbank, you can abuse and get away with it.

Beyond knowing how tender they are, if you’re into chip-stock then blackspot bruising is very important, and you need to know if that variety has issues with bruising because you can’t pick that up easily with our standard bruise test. You try to do your homework before you plant a variety, especially if someone says the variety bruises easily and you’ll have a hard time getting it home.

MV: We’ve significantly increased the acreage of two new Frito-Lay varieties over the past five years. Both varieties have excellent bruise tolerance built in genetically, which has been a big bonus for us as far as increasing the flexibility of where we put some of the potatoes. On the public/private side, Dakota Pearl is our highest acreage non-Frito-Lay variety in our portfolio. It has one of the best bruise tolerances in the chip-stock line-up and that is one of the reasons why we’ve grown so much of it. It has brought down our bruise risk and incidence quite dramatically.

Another public variety we’ve ramped up recently is Monticello. It has a long-season storage window and from a chipping standpoint, it has been a very good variety. However, it has also been a challenge for us from a handling standpoint because it is very susceptible to bruising. We watch pulp temperature, skin-set and maturity, and we try to plant that variety early.

AK: We grow mainly Russet Burbank and Shepody. We’ve tried Alpine, Sage and Clearwater Russets. Vine-kill timing may be different between varieties. Last year, we seeded late, so I didn’t apply Reglone on the Burbanks until later on because they needed some volume, but the Shepody grew quite quickly; in fact, they overgrew. It’s always hard to judge when to desiccate the vines because some years the tubers still gain 25 to 30 per cent bulking up when you think you’ve killed the vines, but some years they won’t.

TG: The coloured varieties are the hardest to minimize bruising on, or it shows up more. For example, we might get the same amount of bruising in a Russet as a Kennebec, but it seems to show up more in the coloured ones—the yellows and reds. If we get a complaint about bruising, 90 per cent of the time it’s on reds, yellows or whites. Yukon Gold is a great variety, and it does well for us, but it can also be a nightmare if you’re not careful. On red and yellow varieties we’ll also use water on our harvesters to keep everything moist—we find that helps a lot.

SS: What is the importance of harvester settings and adjustments to those settings to minimize and prevent potato bruising?

GL: I don’t like any more drops than are necessary. I also don’t like running chains empty. We would normally try to run them slow enough so that the potatoes aren’t jumping on the chains. Usually we prefer running the chains fast enough to keep them filled with potatoes and clay because once you start emptying the chains out you have to be really careful that they’re not bouncing things around.

What applies to a harvester also applies to a windrower. You can’t just check your harvesters, you also have to check your windrowers—the harvester is a bigger machine with more points, but they both have issues. You must have good windrower operators in the same way as you would have good harvester operators.

MV: We constantly look at belt speeds, drops and rollback throughout the day. We play a little bit with the ground speed of the harvester itself, and that tends to adjust the throughput as soil and moisture conditions change. I like to see belts running as slow as possible so that the potatoes are not bouncing along the primary and secondary—often when things are run too fast or aggressive, the potatoes act like popcorn jumping around.

Although windrowers can cause a lot of bruising, we can’t dig our whole crop with just a harvester alone from an efficiency as well as a volume standpoint. When you don’t have enough potatoes to go over or if you’re just digging two or four rows, the windrower helps reduce bruise by putting good capacity over the harvester.

We’ve also invested in harvesters with airheads for removing stones.

AK: One machinery adjustment I make is wind—how much fan volume you’re using with the damper. If everything is sifting out well, you don’t need as much wind, otherwise you’ll blow the potatoes off. It depends upon what stage the vines are at—when the vines are nicely dried up [is best], but by that time I’m basically done. That’s the problem, by the time it’s good going, you’re done.

I don’t like windrowing because there’s so much extra handling and tumbling of the potatoes. The only time I windrow is when we’re starting into a field. Other than that, in my opinion, you’re just increasing the possibility of injuring the seed. You might not notice it in the field, but you sure do notice it in the spring.

TG: We often make adjustments. Almost all fields and varieties require some adjusting and operational changes. The variety and field conditions dictate how you’re going to operate that machine.

Make sure the operator has a good speed so there is no rolling on the harvester. The chains should be full. We don’t go in the hoppers, we go straight into the truck; therefore, the truck and harvester drivers have to be coordinated and we don’t have a big drop going into the truck bin.

At this time we don’t use windrowers. Presently, we’re using Grimme harvesters with Multi-Sep Separator and segment rollers, and we find those are very gentle on potatoes. We’ve done a lot of testing on those harvesters and we feel we have them down to very little bruising. If you look at the harvester industry in the 1990s—let alone harvesters made in the 1960s—and what’s available now, there’s no comparison. The marketplace is so tight for growers that if you’re not just about perfect [in production] and you’re not diligently going after new equipment, you’re out the door.

At the end of the day, if you don’t invest in your people and your equipment you’ll be on the outside looking in very shortly.

SS: What has bruising cost your operation? What adjustments have had the greatest positive influence on your bottom line?

GL: We’re a fresh-pack operation. We specialize in high-quality potatoes, so any time we get bruising it costs money. We do our very best to make sure nothing slips through the cracks. Sometimes when it’s late in the season and temperatures are going to get colder before they get warmer and you’re doing 15 per cent bruise—there’s nothing you can do about it. The machines are all tuned up and you’ve done everything you can, and you’re still taking in 15 per cent—that can happen just because the ground’s too cold or the crop’s not ready, but the season says you have to take it regardless.

The one thing that makes us more money than anything else is constant bruise testing. You spend all year growing the potatoes—you spray them for blight, you’ve got storage lined up, and you’ve got bruise at 30 per cent and you have to throw them away. What was the purpose of that? To my mind, you’ve got to keep that bruise down, preferably under three per cent. You have to do bruise testing and you have to believe in it, and when it says you’re bruising, you have to respond to it.

MV: Mechanical damage and under-the-skin bruising increases our external defects. Once we have injury, we also have a higher incidence of fusarium dry rot. The incidence and percentage of bruising really starts to rear its ugly head once we get into later storage windows—March and on.

Our biggest bang for our buck has been talking to growers about bruising—just telling the story of the bruise and how it impacts the bottom line. We’re trying to empower our growers and push them toward innovation. There used to be lots of different companies, prices and qualities, but now every company wants to do the same—drive quality. We’re trying to push that back to our grower group. The most important thing is to pay attention to it 24/7—there are no magic answers. It’s all the little things along the way from start to finish that are going to make the biggest impact.

Every grower wants to harvest every day to get done quickly, but there are some days you probably have to stop. It’s cheaper to pay your employees to stay at home than it is to harvest potatoes under poor conditions.  Taking a day off through the harvest is a very difficult decision to make, but probably one we need to make more often.

AK: We keep [the crop] until spring, so anything that is damaged is noticeable and gets thrown out. I don’t ship out until April and May and by that time when you look in the shed and you see how many potatoes are possibly rotting, you know how you treated them [at harvest]. Any type of injury will show up by springtime.

For the past couple of years, one of the last sprays I’ve been applying is Acrobat because of late blight issues. It’s supposed to be good for the health of the tuber, and it seems to be [working]. I was expecting a 10 per cent throw-out this year, and even with the oversized, I don’t think it was over three per cent—in the end I had more to sell in the shed than I’d planned on.

TG: Since we’ve updated our harvesters, probably the next best thing we’ve done over the past 10 years is convert our storage sheds to refrigeration and controlled humidity. Without these changes, I don’t think we’d be able to ship quality potatoes after February. I see the difference from what we could do 10 years ago to what we can do now with respect to controlling humidity from the day the potatoes go into storage until the day they come out. To me there is no bigger advantage, and it’s not that expensive when you compare it to a potato harvester. If you’re going to store potatoes past Christmas, you better have refrigeration and humidity control. The yellows and reds we took out of storage in early May looked nearly as good as the day they came out of the field. If you don’t have controlled humidity and refrigeration, I believe you’re at a disadvantage.

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