Features Agronomy Corn
Trait advantage varies: recent findings question the need

Genetically modified traits for corn are becoming ubiquitous. Roundup Ready, Liberty Link, corn borer, corn rootworm, western bean cutworm, double stacks, triple stacks, super stacks – the options seem limitless. However, some growers are wondering if the extra costs to buy this seed are actually resulting in a yield advantage that gives more bang for the buck. As it turns out, that is a difficult question to answer.A number of people have probed this topic; the latest investigation is a field project funded by an Ontario Soil and Crop Improvement Association regional partner grant involving Essex, Kent and Lambton counties in southwestern Ontario. “It’s very much a grower-driven project,” says project lead Adam Hayes, soil management specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). He explains that some of the association’s growers say they have been planting conventional hybrids and getting great yields at low seed cost. However, seed companies are offering fewer conventional choices and moving to higher-priced seed with multiple traits. The growers wanted to evaluate if there is an economic advantage to switching from conventional hybrids to those with traits.

To do this, the project basically compares net income based on seed costs and yields (assuming $4.50-per-bushel corn) for several hybrid sets. A hybrid set has similar base genetics but different trait packages. For example, a hybrid set might comprise a hybrid with no traits (conventional), the same hybrid with one trait for herbicide tolerance (RR), the same hybrid with one trait for European corn borer (ECB) and the same hybrid with three traits for RR, ECB and corn rootworm (CRW). “When we started out, the idea was to have a hybrid without the traits and then the equivalent hybrid with one or more traits in it to compare. And that’s become more difficult each year with the project,” Hayes explains. He says this is because fewer conventional hybrids are being marketed and because some of them have different base genetics and do not fit into a set. “So the check has often been a Roundup Ready hybrid, rather than a hybrid that doesn’t have any traits in it.”

Country Farm Seeds, Dekalb/Monsanto Canada and Maizex donated seed for the project. 

Preliminary results
Based on yields and seed costs, Hayes found more of an economic disadvantage than an advantage of using traits in preliminary results from 2009 and 2010. For three hybrid sets each year averaged over multiple sites, only one set showed an economic advantage, and that was for the RR trait and the RR-ECB-CRW triple stack over the conventional. Calculated net losses of planting hybrids with traits were in the range of $11 to $40 per acre; net gains were $11 to $12 per acre.

However, Hayes points out that a hybrid set could show differences in economic performance at different sites. “In 2010, we did have a set of Country Farm hybrids where there were no traits, one ECB, one RR, and a triple stack as well. At one site there was no advantage to the RR, and at the other site there was a pretty good yield advantage to the RR.”

He also notes differences between the two years for the same site. As an example, he says, “There was a site north of Thamesville where, the first year, there was some advantage to the traits, but then the second year, there wasn’t an advantage to some of the traits.”

A previous study by two Agriculture and Agri-Food Canada researchers compared conventional hybrids and similar hybrids with the ECB trait under natural ECB pressure. The research took place in the Ottawa area during the 2000 to 2002 growing seasons. Their published results say that on average, they found “…no yield advantage of Bt hybrids in comparison with their conventional counterparts when stalk lodging and breakage of the non-Bt counterpart by ECB was low to moderate.”

Another study by four researchers at Cornell University in New York during the 2007 and 2008 growing seasons compared sets of a conventional hybrid, an RR-ECB double stack, and a RR-ECB-CRW triple stack. Comparing yield income at $4.67-per-bushel corn along with seed, grain drying and herbicide costs, they found the economics were highly site dependent. They concluded that stacking the Bt traits with RR “may not always be justified,” as three of their eight comparisons showed a profit, three broke even and two showed a loss. They suggested, “…growers in New York should carefully match each hybrid trait to their specific fields and not buy Bt stacked hybrid traits indiscriminately because of their availability…”

What does it mean?
There is value to traits that cannot always be measured in this type of experiment, says Greg Stewart, OMAFRA corn specialist. He has compared conventional and RR corn in past Ontario Corn Committee hybrid trials. As an example, he says, “In the broader, real-world situation, there probably is some value to having glyphosate-tolerant corn. In the context of a farmer using it, there’s simplicity, there’s a wider window of application and there’s better control of a broader spectrum of weeds. But if you tried to examine that in carefully done trials like we’ve done, you end up finding that the conventional chemistry applied on time, on target, et cetera, does just as well.

“I think out of the three possible technologies that we’re talking about – herbicide tolerance, rootworm control and European corn borer protection – I think it would be easiest to argue that the ECB actually has value (for Ontario growers),” he states. Stewart says that is because there really was not a good way to control ECB economically before the Bt trait was introduced, so growers were taking a six- to eight-bushel yield loss. In contrast, insecticides applied through the planter were used to control CRW for the few corn-on-corn acres in Ontario.

These studies suggest some good news for producers using the Bt traits, who are required to plant refuge acres. Taken together, the results of these studies indicate that, unless growers are in an area that is prone to heavy ECB infestation, the net economic result from the refuge acres should not be much different than that from the rest of the acres. “There are lots of refuge hybrids that are pretty competitive,” says Stewart, “as long as it didn’t happen to coincide with an onslaught of ECB or if perhaps you didn’t get harvested on time and you had stalk breakage.”

ECB feeding can contribute to stalk breakage. “If you can get it harvested relatively early, the loss is pretty small. You could take that same area of the province with the same relatively high ECB pressure, put in a different hybrid that maybe has poor stalk strength, and make it the last field you harvest instead of the first field you harvest, and now the losses are going to look much worse.”

And indications are that ECB numbers have gone down since the Bt trait was introduced, say both Stewart and Hayes. “There aren’t the same numbers of corn borer around as there were say, 10, 15 years ago,” says Hayes, “so the refuge shouldn’t be suffering as much as it would have 10 or 15 years ago.”

John Waters, a certified crop advisor with Lakeside Grain and Feed in Lambton County, says that growers should be using traits “all the time. Our biggest trait users would not be using it if they didn’t think there was a payback.”

He notes that many growers in that area believe that they would not be able to grow corn if the traits were not available.

Hayes has different ideas. He emphasizes viewing the traits as tools and paying close attention to site characteristics. “If you have a field with a particular issue, pick the traits that fit for the various situations,” he recommends. “What we’ve shown for the most part hasn’t shown much economic value to some of these traits, in trying to average it out. But it’s more the individual situations. There are field or farm situations where it makes sense to use those traits, either from an insurance perspective or just from the management system that fits better for a particular operation.”