AgronomyBMPs for Potato Fertilization

BMPs for Potato Fertilization

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[deck]Successful growers from across the country share their thoughts on Best Management Practices in potato production.[/deck]

We posed the question of BMPs for potato fertilization to three growers from across the country: Manitoba’s Chad Berry, Bill Vasily of Ontario and New Brunswick’s Carl Stephenson. Here are their views on the best of the BMPs.We are pleased to present the second edition of ROUNDTABLE, Spud Smart’s special series in which we ask growers from different regions of the country for their insights and opinions on Best Management Practices in potato production. Planting season is almost upon us, so we thought growers would benefit from knowing tricks of the trade from other farmers for fertilizing potatoes and getting the 2014 crop off to the best start.

Soil and Tissue Testing

Stephenson maintains it’s important to do the diagnostic legwork, in the form of soil testing and plant tissue tests, to ensure the right nutrients are being applied in the right amounts and at the right times each year. To this end, an initial soil test is good way to get your plants off to a good start.

“First of all, you need a good soil analysis to make sure everything is up to snuff on your ground,” he says. This year, Stephenson plans to do soil testing using a grid pattern on a portion of his potato acreage, to help identify which areas of the field may need more nutrients, and which ones less.

“That’s going to be something I’m going to implement into my fertilization this coming spring…. I think I’m going to be able to save in the long run,” he says.

“When we go to lime, there are places that won’t need any lime applied in certain areas of the field, and others that might take 3,000 pounds [of lime] per acre,” Stephenson says. “What’s been done a lot in the past, is you just go and apply a standard [amount of lime] per acre on the whole farm. Well, there’s part of the farm that [doesn’t] need it. So hopefully this will pay off.”

Stephenson said this new practice could also mean having to use less fertilizer when he applies his first nutrient mix at the start of the season. “I might be able to broadcast upfront some of my requirements for fertilizer, then I have to put less down the tube at planting time with my potato planter,” he says. “I’m hoping to see some results from that in the next few years.”

Vasily says he doesn’t do as much soil testing as some potato producers, but a lot of that has to do with the type of ground he farms on. “I’m on a very sandy soil. I’ve been farming this soil for a long time, and every now and then I’ll soil test, but … after 30 years [the results are] almost identical, so you’re really just monitoring pH of the soil,” he says.

“But I do it every now and then just to keep an eye on what’s happening with the nutrient levels.”

Stephenson makes a point of ensuring his potato plants are checked regularly during the growing season. “I have petiole tests done every two weeks when the plants get to a certain stage.… It just lets me know what’s going on in the field,” he says.

“If we’ve had a significant amount of rain in the early part of the season, maybe the nitrogen level’s not where it should be, so I can apply some more [nitrogen] in the sprayer.”

Berry agrees that regular plant testing is an important BMP. “We petiole test every week and that’s how we decide what we’re putting on later in the season,” he says. “You can put on an application that’s going to meet the crop’s need, and that’s it.”

Vasily says he’ll do plant testing if there’s a problem in the field but “I don’t do it as much as I should, perhaps.” He believes measures like petiole testing are  “actually a very good thing to do” because they help growers “keep track of the nutrients that are in the plant.”

Using Micronutrients

Berry says he uses foliar applications of micronutrients in-season to boost his crop’s potential. This way, he says, you’re using “just enough product,” which not only saves money but also results in better yields and improved crop quality.

Vasily adds magnesium sulphate and the micronutrient zinc (in the form of zinc sulphate) to his blight spray mix during the season to supplement his fertility program. He also applies boron to the soil in the spring.

Stephenson believes zinc and boron are important micronutrients for potatoes, but in the past he’s had difficulty getting just the right amount in his fertilizer mix.

“Previous to the last few years, if you wanted boron or zinc added to your fertilizer blend, it was kind of thrown into the mix,” he says. “It was such a small amount that my agronomist and myself came to the conclusion that we didn’t really think we were getting any advantage out of it.”

Timing was also an issue. Stephenson says boron in particular is helpful in controlling hollow heart, and for this reason he’d been applying it foliarly to his plants in-season. However, the boron application had to be at a certain stage in the plant’s growth, and getting the correct timing was tricky.

Stephenson says the fertilizer company he’s working with now has come up with a new process “where every aspect of your fertilizer [applied at planting] should have a certain portion of your boron and zinc in it.”

Stephenson plans to implement the new process this year. He doesn’t know exactly how much it’ll cost yet, but Stephenson figures it shouldn’t be any more than what he’s paid in the past to apply micronutrient foliar sprays in-season.

Application Methods

Berry uses variable rate fertilizer application as an upfront treatment prior to the growing season. “We use it to maximize yield and try to create a more uniform crop across the field,” he says.

After this initial variable rate application, Berry will use a top-dressing on his potatoes in-season, followed fertigation for finishing.

Berry says spreading out his fertilizer applications at his irrigated farm helps reduce environmental impacts associated with runoff. “That’s why some of the fertilizer will go on in the spring, some will go on at hilling time, and then the rest will go on through the pivots in-season,” he says.

Many potato producers these days use broadcast fertilization methods, at least for some of their applications. Stephenson says some farmers in his area start their fertility program off with a broadcast potash application each fall or spring. “I usually haven’t done that,” he says. “Most of my [fertilizer] blend just goes right down with the planter at planting time.”

Vasily doesn’t use broadcast methods either. “I’m in the minority now, but I think the placement of the fertilizer is very important,” he says. Vasily believes targeted fertilizer applications, unlike broadcast methods, put the nutrients where they’re needed most.

“If it’s broadcast, it can be too high, too low, too far into the middle of the row, and that type of thing,” he says. “My placement is totally around the plant root zone. The fertilizer is put where the roots can access it the earliest, and also it’s in that potato hill which protects it from leaching.”

Vasily says his first fertilizer application is in the spring, “when we just go in with a planter to a pre-bedded fumigated sub-soiled hill. We apply the fertilizers through the season — there’ll be the band at planting, there’ll be a side-dress at hilling time, and then there’ll be a top-dress before row closure, mostly nitrogen. So there’s different layers of fertilizer, but all in the root zone, and there are different times of application.”  Vasily adds that with exception of micronutrients, granular fertilizer is used in all of soil nutrient applications.

Vasily acknowledges that one of the reasons broadcasting fertilizer has become so popular is the increasing size of farms. He’s a 300-acre grower, while many of his counterparts are farming 1,000 acres or more of potatoes. With operations that size, time is usually of the essence.

“They want the speed so they’re broadcasting fertilizers, whereas my method perhaps utilizes the fertilizer better,” he says. With rising concerns over the impact of nitrogen runoff into streams and lakes and resulting algae blooms, Vasily forsees the day when farmers may be required to be much more conservative in their nutrient usage.

“I know it’s going to be very hard to convince farmers not to broadcast fertilizer, but that’s one of the biggest things, I think.… We’re wasting nutrients with that method,” he says. “I do think we have to learn how to use the least amount of these [fertilizers] and produce economic results.

“I think I’m already doing the best I can by putting [the fertilizer] where it can be utilized most efficiently,” says Vasily. “I honestly can’t think of a better way to do it with the acreage I’m running.”