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Researchers abuzz about soybean yields

The research is preliminary, but early results suggest that some bees might be good for soybean crops

Some call it serendipity. Others say it merely proves the old adage that you make your own luck. Either way, some of the world’s biggest scientific breakthroughs have come when the researcher was actually looking for something else. Think penicillin, for example.

Matt O’Neal is more a member of the group that says it all boils down to hard work, and knowing how to make use of what you find. As an assistant professor of entomology at Iowa State University, O’Neal has been involved in several studies on bees and their impact on, unexpectedly, soybeans.

Despite the long-held view that soybeans are self-pollinating and therefore don’t need an insect to move their pollen about, O’Neal has been looking at conservation practices using prairie plants and other species that could entice beneficial insects.

The work started with searching for beneficials to combat soybean aphids. Now, it’s directly focused on what impact bees might have on soybean yield.

But it isn’t an overnight project. It started a decade ago, and continues today.

“I started at Iowa State in 2004, and I was hired during an outbreak of the soybean aphid,” says O’Neal, adding that some of his early work examined landscape factors that could help researchers understand where and when an aphid outbreak was occurring.

“One thing we learned in the first five years — from 2004 to 2009 — was that the landscape around soybean fields helped predict the risk for a soybean field. And what we learned over the course of several studies was that there’s a community of beneficial insects — predators — that will feed on the soybean aphid, and if given the chance, under certain conditions, can prevent outbreaks from occurring.”

At the same time, another group of researchers were taking a comprehensive look at incorporating strips or small areas of prairie plants into a watershed or catchment area that grows corn and soybeans.

Their goal was to see if those strips would reduce the amount of sediment loss coming off those fields, and reduce the amount of nitrate and phosphorus moving out of those fields as well.

A second question would then be, if you have these prairie strips, would you see more beneficial insects in them, and would their benefits spill over into adjacent crop fields?

Beneficial insects include pollinators such as bees, and some of the sampling techniques that O’Neal and his students used caught bees almost by accident.

Mistaken identity

It’s worth noting that nearly two years ago, there was a citation in a U.S. farm publication of a similar Canadian study on the effect of honeybees and higher yields on food-grade soybeans. But O’Neal says that the particular citation was incorrect, and that the work was actually done in Brazil.

In those trials, researchers set up bee-proof cages in large soybean fields during flowering, says O’Neal. The team then compared yields from plants that were caged against plants that were visited by bees. They found about a six per cent increase in yield when the bees had access to the flowering soybeans.

These bees would be a combination of several species, not limited to honeybees. So in another part of the field, they placed eight honeybee hives and they repeated the experiment.

With the honeybees nearby, the soybean yield was 18 per cent higher.

On the surface, the take-home message would be that soybean yields respond to bees, and that when researchers controlled for the type of bee, they could get a different yield response.

But there was a problem, O’Neal says, because the research wasn’t adequately replicated. There was one large field and the “replications” were the caged plants, not another field test conducted under the same specifications.

O’Neal says he’d regard that study as successful in indicating some evidence to support the hypothesis that bees can improve the yield of soybeans. But it’s mainly a starting point, not the basis for making specific changes in farm management practices.

“How do you tell a farmer in Iowa how to take advantage of that?” asks O’Neal. “How many honeybee hives would it take, and for how long should the plants be exposed? Think about science breaking down between biological and management when it comes to agriculture. Biological studies show what’s possible, but when it comes to management, you have all kinds of questions how. It’s kind of not yet ready for prime time to think about how we would incorporate honeybees into soybean production.”

In the last three years, O’Neal has been studying the community of bees that visits soybeans and corn, and honeybees are there, but they’re not the most abundant bee in the soybean-growing region in North America. In fact, O’Neal has seen a community that encompasses at least 40 or more bee species. And not all of them forage on flowers.

Even so, when O’Neal and his colleagues focused their attention on the most abundant bee species, anywhere from 20 to 30 per cent had soybean pollen on them. That suggests that bees do use soybeans as a food source, even though there are probably forage sources out there that they prefer. It seems that if better food isn’t readily available, they’ll go with what they can get.

“There can be, at times, a lot of soybean flowers available to bees, and not just honeybees. There are probably some species that can do well in those landscapes,” says O’Neal. “But that’s a huge black box that nobody knows much about, and we’ve only scratched the surface. When we look at the bees that we capture, a subset of them has corn and soybean pollen on it, and that gives us some insight that, yes, these bees are probably there for the corn and soybeans.”

Not all the reaction to his research was positive, but as he has continued to pull evidence together, more researchers have gotten involved, and now there is interest in Ohio, Kansas and Manitoba — even in China — for doing local research.

What’s interesting, especially in North America, is that they’re finding many of the same species of bees everywhere they look. In conducting the research in other regions, O’Neal learned that Manitoba has the greatest number of honeybees in its soybean fields, while Kansas has the most diverse community of bees.

Asked if the preliminary results indicated any sign of a yield bump in soybeans due to the presence of bees, O’Neal replies that the research wasn’t designed to do that. Instead, it would provide an understanding of the bee community and the best way to measure its abundance and diversity.

Indiana research

Christian Krupke, associate professor of entomology at Purdue University is leading an effort among north-central entomologists focusing on which species of pollinators are present, and how far they fly into the field.

One of the perceptions about bees revealed in the recent debate concerning neonicotinoid-based seed treatments is the assumption that all bees are honeybees, which is not true. Determining whether they are a native species or if they are domesticated can create multiple layers in the research for both Krupke and O’Neal. If the bees are native, as O’Neal states, there are as many as 40 different potential species.

“There are many species of native pollinators that have been here since long before we got here, and are specialized on crops and flowers of different sizes and shapes,” says Krupke. “In many cases, they’re more efficient than honeybees because they’re tiny, they can get right into that flower, they can buzz their wings to pollinate and they’re far more adapted to certain plants.”

Yet little is known about these species. Nor do researchers know how to raise them in large quantities. As well, it’s hard to determine where they are, and the kind of a nesting habitat they like.

The other problem is that most of them are solitary species, which makes it difficult to increase their numbers and use them for agriculture of any scale.

“If we go 100 metres, 200 or 500 metres into a field, the number of bees may drop dramatically, because that’s a long way to go into a crop that doesn’t offer a lot of resources to a bee,” says Krupke. “If they do have an impact, it may be restricted mainly to the edges of large fields, because they just can’t go far; they’re too small and there aren’t enough of them. If we don’t find any bees in our surveys that extend 500 metres into the field, then there’s the answer — they’re probably not affecting yield.”

Stretching the limits

O’Neal believes there’s much more to the issue of bees and soybean yields, which is why he’s looking into the diversity created within a comprehensive management program. Working with other researchers as part of the STRIPs group — Science-based Trials of Row-crops Integrated with Prairies — he hopes to develop an overall approach that looks at the impacts of surface-water management, erosion control and prairie strips.

“The trick is, you’re looking for those efficiencies that you can build along similar lines,” say O’Neal. “For me, if I had a menu of practices and I was trying to select ones that are most important for pollinator conservation, habitat and improved forages would be at the top. Below that would be reducing the exposure to pesticides, and below that cover crops.”

There is definitely a soil-health component to growing cover crops, but O’Neal suggests it may be minimal advantage to conserving bees. Cover crops scavenge residual nutrients and they might provide a little microclimate that’s better than bare soil for ground-nesting bees, but in the end, the cover crop will be “burned down” or tilled.

As for incorporating prairie strips on a farm, the challenge is to prove there’s a payback for farmers. Right now, the STRIPs group has some 20 farmers interested in taking part in this research. However, U.S. farmers also have access to local, state and federal programs, including the Conservation Reserve Program (CRP) that can help offset the value of production being set aside for the prairie strips. In Canada, a similar opportunity isn’t as readily or widely available.

About the author

CG Production Editor

Ralph Pearce



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