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Are two hybrids better than one?

An Ontario project is exploring the idea of mixing a later hybrid with a normal-season hybrid in a field to improve yields and drought-proof the crop. Photo courtesy of B. Rosser, University of Guelph.

Could mixing together two corn hybrids of different maturities boost your yields and help drought-proof your crop? That’s the intriguing question corn specialist Greg Stewart is exploring in a small project.

Seeding two corn hybrids together in a field has been examined in various studies over the years based on a variety of different ideas of how mixing might enhance yields. Stewart’s project is looking at three concepts.

One idea is that mixing could reduce the risk of pollination problems due to dry conditions. For good pollination, the timing of the pollen coming off the tassel needs to line up with the timing of the silks being receptive to pollen. “But in dry weather, sometimes that synchronization gets pulled apart – the pollen supply gets earlier and the silks get later. So the pollen sometimes dries up before the silks emerge,” explains Stewart, who is with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).

“One approach to this problem is to mix a small percentage of a later hybrid in with your normal hybrid. If stress conditions occur, then that later hybrid might have pollen flying around when the majority of the field perhaps is still looking for a little more pollen.” Corn yields can be severely reduced if pollen shed and silking aren’t synchronized, so this approach could provide some valuable weather proofing when conditions are dry.

Another idea is that mixing in a small proportion of a longer-season hybrid might give a bit of a yield boost without too much added risk. “Most growers realize that full-season hybrids have a yield advantage but also some risk in terms of higher moistures or perhaps the crop not making it to maturity,” Stewart notes.  “Rather than planting the entire field in that riskier, super, full-season hybrid, you could plant perhaps 20 or 25 per cent of the field to that hybrid. So you’re taking a bit of risk, hoping for some yield improvement, but it’s not as risky as planting the entire field in that long-season hybrid.”

A third rationale for mixing different hybrids is that it might provide out-crossing benefits. “Sometimes if the pollen from one hybrid lands on the silk of another hybrid, there can be an effect on kernel size or other kernel quality. If you could get the right combination of pollen from one hybrid and silks from another hybrid, then you could have a little yield improvement. But it’s a bit of a long shot to find some sort of magical pairing between hybrids,” Stewart says.

In this current project, Stewart is focusing primarily on the first two concepts: “I am dabbling with this idea of putting long-season hybrids in with normal-season hybrids for a given field,” he says. “I’m looking at the impacts on yield and harvest moisture, and I’m observing the pollen supply-and-demand scenario.”

Stewart started the project in 2013 with three Ontario sites. He was only able to establish one site in 2014 because of the ugly spring weather. The Water Resource Adaptation and Management Initiative of Farm & Food Care Ontario provided funding for the first year.

The project’s three treatments are a normal-season hybrid planted alone, a long-season hybrid planted alone, and a mixture of the two hybrids planted together. The later hybrid silks about five to eight days later than the normal one.

To blend the two hybrids in the mixed plots, the six-row planter used for plot seeding is set up so that rows 2 and 5 are seeded to the long-season hybrid, and rows 1, 3, 4 and 6 are seeded to the normal-season hybrid.

It hasn’t been possible to evaluate the pollen synchronization idea so far because dry weather stress didn’t occur in 2013 or 2014.

The preliminary results suggest there might be an advantage to the risk reduction idea under certain conditions. In 2013, at one of the three field sites (Bornholm, see table), the blend gave a significant yield boost. Although the moisture content for the blend was higher than for the normal-season hybrid, the yield boost with the blend was large enough to more than offset the extra drying costs. At the other two sites, there was no advantage to the blend.

Tips if you want to try it
If you’re thinking of experimenting with this concept, Stewart offers a few tips. “First, choose your normal top hybrid. Then choose a hybrid that is about a week longer, or is going to silk about a week later, or has a rating about 150 heat units higher than your main hybrid.”

Then choose what proportion of the field you’d like to have planted to the full-season hybrid. “I’ve been seeding about 25 per cent of the blended plots to the later hybrid, but I think it could be a lot less, perhaps five to 25 per cent of the field,” says Stewart.

Finally, decide how you want to mix the two hybrids together in the field. Although Stewart has been planting them in separate rows for ease of measurement in his project, he thinks there might be an advantage to physically mixing the two hybrids together before putting the seed in the hoppers. “We haven’t tested that, but I think if it turned out that you needed the pollen supply, then having the long-season hybrid completely dispersed throughout the field might give you a better advantage. The yield and the moisture content are not going to be affected by how you mix the hybrids.”


November 3, 2014
By Carolyn King

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