USDA-ARS tests indicate that planting two genetically different corn hybrids in the same field can raise yields and increase protein content. ARS scientists say that's due to cross-pollination.

Seed company researchers, however, maintain that mixing hybrids probably isn't practical.

ARS scientists, in cooperation with a group of farmers and Centrol, a crop consulting firm, conducted trials in 1997 and 1998 near Morris, MN. When hybrids from different companies were paired in the same field, they yielded an average of 4 bu/acre more than the same hybrids grown separately. The highest-yielding pairs also produced up to 0.4% more protein.

To implement paired plantings, farmers need to plant two unrelated hybrids in alternating rows or mix them in the seed hopper. That's the advice of ARS plant physiologist Mark Westgate, who led the paired-planting project.

"This is an old concept, but it works," says Westgate. "Even though the yield advantage is not large, it adds up when spread over an entire farming operation. The key is to plant two unrelated hybrids that shed pollen at the same time. Farmers need to ask seed companies for hybrids of different genetics."

Scientists at Pioneer Hi-Bred Int'l. agree that farmers need to plant a package of hybrids with different genetics. They also agree that the theory of achieving slightly higher yields through cross-pollination is sound. Nevertheless, they question the practicality of that option.

"To achieve yield gains, the two hybrids would need to both pollinate and reach harvest maturity at the same time," points out Pioneer's Paul Carter.

Several university research trials indicate that mixing hybrids doesn't pay.

University studies going back to 1959 in Ohio and 1964 in Iowa found no yield differences between pairs of hybrids planted together vs. hybrids planted separately.

In more recent studies (1978-79) at the University of Guelph, Ontario, hybrid mixtures never outyielded the highest-yielding hybrid in the mix. And a 1998 trial in Ottawa, Canada, found that mixed hybrids had no yield advantage over pure stands of each hybrid.

Paul Groneberg, Centrol consultant at Donnelly, MN, who cooperated in the 1997-'98 ARS yield project, says the idea of mixing hybrids is good in theory but it hasn't worked quite as well as he'd hoped.

"The challenge is to find the right pairing of hybrids," says Groneberg. "There needs to be a massive screening to find the two hybrids that have the most yield impact when paired. And because hybrid turnover is so rapid these days, the screening would need to be ongoing."

Pioneer's Carter points out that corn genetics are improving by 1-2% per year. By the time the right mix of hybrids is identified, growers gain as much or more yield by separately planting several new hybrids with different genetic backgrounds.

ARS' Westgate, however, maintains that by mixing two unrelated hybrids, one from a lower price bracket, a farmer could get a comparable or better yield while saving money on seed.