Drought-tolerant corn hybrids were welcomed with expectations that they could withstand a drought by surviving until the next rain, much like a camel plods to the next oasis. Farmers and researchers are finding that metaphor to be basically true, but the race to the next water hole may sometimes be a close call.

“We’re finding that in moisture limited situations, drought-tolerant hybrids have fared well, but results have been variable from year to year and depend on which hybrids are compared,” says Alan Schlegel, agronomist at Kansas State’s Southwest Research and Extension Center. “Some traditional hybrids are well adapted and perform nearly as well even in stressful conditions, so hybrid selection is an important factor.”

Generally, K-State’s four years of research have shown that a slight yield advantage to drought-tolerant types begins to increase as the yield of the regular hybrids falls below 150 bushels per acre. At yields above that level they’ve found no significant yield difference between the two types.

“It’s important to note that our results have varied widely depending on how individual hybrids have responded to drought stress,” says fellow agronomist Kraig Roozeboom.

“Our results varied. We sometimes saw no difference between the two types at yield levels down to 100 bushels per acre, but other times saw a distinct advantage to drought-tolerant types under stress and a slight edge to conventional types under favorable conditions. While the performance of individual hybrids may vary, it’s reasonable to expect the drought-tolerant types to serve as an insurance policy to sustain yields under dry conditions,” he adds.

Three choices. Drought-tolerant hybrids are offered by Syngenta (Agrisure Artesian), Dupont Pioneer (Optimum AQUAmax), and seed companies associated with Monsanto (DroughtGard). DroughtGard hybrids were developed through genetic engineering while the other types resulted from traditional breeding techniques utilizing cutting edge molecular tools.

“The companies argue about which is the best approach, but we’ve used both and haven’t seen a lot of difference,” says Colby, Kansas, farmer Aaron Horinek. “We’ve planted  AQUAmax hybrids since 2010 and DroughtGard since 2012 as well as  some traditional hybrids that have performed well under stress for us.”

The various hybrids get a good stress test on Horinek’s dryland operation, which receives an average annual rainfall of 20 inches. “We have a very aggressive rotation and grow a lot of corn on corn. Yields obviously suffer in dry years, but the fact that we can do it at all is a testament to how the drought tolerance of all hybrids has been improved in the past five years,” he says.

“We plant our whole farm in split-planter fashion so hybrids are compared side-by-side across entire fields. When yields fall below 70 bushels per acre we’ve seen some advantage to  DroughtGard hybrids, but it’s usually  within the margin of error we expect from our yield monitor,” he adds.

Pilot Point, Texas, farmer Jeff Weber thinks drought-tolerant hybrids may aid his plans to double-crop corn after wheat. “We’re typically hot and dry in mid-summer, but we’ve got a lot of growing season left. We tried it last year with an AQUAmax hybrid, and though conditions were unusually harsh, it still made corn while regular hybrids simply died,” he says.

More results. Researchers at Texas A&M Agrilife tested Artesian hybrids in a four-year study with irrigation at 50%, 75%, and 100% of the evapotranspiration (ET) needs at three plant densities. At 50% ET, the drought-tolerant hybrid out-yielded others by 8% with 24,000 plants per acre. It out-yielded by 17% at a stand of 40,000.

The chart above shows results from  tests Schlegel did in 2015 comparing all three drought-tolerant products to two conventional hybrids at 60% and 100% ET. “This shows the importance of placing the drought-tolerant technology in hybrids that are well adapted. Under stress (60% ET), one  conventional did very well while the other fell short of the tolerant types. Also, at full ET the drought-tolerant hybrids didn’t drop off,” he says.

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