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Returning to dual-purpose corn

If farmers in Eastern Canada continue to increase their soybean acreage next year, the number of buffer acres that mixed operations allow for corn silage could be tighter than before. In the event of a poor season, there may be value in knowing which grain corn hybrids effectively double as silage.

At one time, all corn hybrids were suited to being harvested for grain and for silage purposes. It wasn’t until silage-specific hybrids were commercialized that the term dual-purpose came into existence, largely for marketing purposes, and the role these multi-use products should play has been hotly contested ever since. In exchange for flexibility, these products typically sacrifice grain yield, silage quality, or both, diminishing their popularity. As Greg Stewart, corn specialist for the Ontario Ministry of Agriculture and Food (OMAF), recalls, silage-specific hybrids were created specifically to respond to the problems posed by dual-purpose options.

“One of the big problems with a dual-purpose hybrid is that the grain characteristics make them harden up and dry down quickly,” he says. “The silage-specific hybrids were designed not to have as rapid starch fill, as high a test weight, or move to black layer as quickly, offering a larger window to get good quality silage that’s not too dry.”

But Stewart says that with today’s analysis methods, there might be evidence to suggest some silage-specific hybrids don’t produce any more milk per tonne or milk per acre than a dual-purpose hybrid with a reasonably good starch digestibility score. And there’s really nothing special, agronomically, to do to achieve that. Dual-purpose hybrids respond just as well as any corn plant does to phosphorus applied in a 2 x 2 inch band (two inches below and two inches to the side of the seed), a starter fertilizer which supplements fertility needs identified by regular soil testing, and excellent weed control between the 4th and 10th leaf stage. But when it comes to harvesting, he can’t offer a magic bullet recipe for good quality silage.

“If we’ve moved away from anything, it’s the idea that all hybrids can be treated the same,” said Stewart. “You’ve got to be more in tune with what silage quality really means and how you assess it.”

If Joel Bagg, OMAF’s forage specialist, had to choose a model of assessment when it comes to analyzing hybrids for forage quality, his first preference is the MILK2006 model from the University of Wisconsin. Bagg doesn’t think it’s fair to make blanket claims about which types of hybrids are better than others because he thinks farmers need to look at each individual hybrid based on the data available. He refers to well-run silage hybrid trials conducted in the United States.

“Other than brown mid rib, there’s not a lot of difference in fibre digestibility across hybrids but there’s a big difference in starch.” says Bagg, “And we have a lot better ability to measure starch digestibility than we did even 15 years ago.”

Dan Undersander is one of the research and extension agronomists at the University of Wisconsin who is working with these trial and forage analysis results daily. The trials don’t indicate when a hybrid is marketed as dual-purpose, but products that perform well as a silage and grain corn are a safe bet even if they aren’t labelled for both uses. Based on these experiences, Undersander now recommends farmers with forage needs grow grain, silage and dual-purpose hybrids every year.

“Dual-purpose is bred for both grain and forage yield so you obviously have to make some sacrifices on both to stay at a moderately high level, but that’s not to say there isn’t a place for it,” he says. “My approach is to recommend a farmer calculate how many tonnes of silage he wants, then how many acres that takes in a good year, plant that acreage to corn-silage hybrids, then plant a buffer of 15 or 20 per cent dual-purpose, and all the rest goes to grain corn.”

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From an agronomic standpoint, he agrees with Stewart that dual-purpose hybrids generally need the same treatment as any other corn hybrid. But since the usual recommendation for silage-specific hybrids is to increase the seeding rate by five to 10 per cent over the rate for grain corn, a dual-purpose rate might be best somewhere in between these rates. The only other challenge Undersander finds in growing dual-purpose is selecting the right hybrid maturity.

“A large portion of the difference between silage and grain crops is simply the maturity,” he says. “For dual-purpose, we’re probably going to want to plant a hybrid that will mature within our growing season, limiting our total tonnage yield, but that still gives us grain at the end of the season if we need to go that way.”

In Canada, Bagg warns that it’s buyer beware when it comes to purchasing silage hybrids for dual-purpose, since most companies breed their hybrids in the United States and may not even have regional performance data. But he also reminds producers that hybrid selection is only one of many things that need to be done right with corn silage. Harvesting at the right moisture, using an inoculant and processing kernels remain key. He also says packing is typically the weakest link in bunker silo management.

“Packing is usually not enough and you might lose 12 to 15 per cent of the silage you put in there to fermentation because the bacteria are actually using some of the dry matter for fermentation,” Bagg says.

Whether farmers are harvesting silage-specific or dual-purpose varieties, Bagg says, there are always lots of invisible losses, which is why forages are so much more difficult than grain crops to gauge yield. He says it’s a loss for Eastern Canada that there aren’t silage corn trials here, but he doesn’t expect to see anything change for the better anytime soon.

“It wouldn’t take much to do corn-silage trials if farmers wanted; the infrastructure is there, but there isn’t the stakeholder willingness to pay for it,” he says. “We’re struggling even to maintain our forage trials.”

February 19, 2014  By Amy Petherick

Silage-specific hybrids were created in response to problems posed by dual-purpose varieties If farmers in Eastern Canada continue to increase their soybean acreage next year


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