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| Here is one study I found on the internet from the early 90's. New hybrids may have different results.
Corn scientists are usually a pretty placid bunch. Apparently, there isn't much in a corn plant that's worth getting riled up about.
Blood pressures are soaring, however, over new studies from Purdue University that say a corn crop's yield will vanish into thin air if the farmer leaves in the crop in the field after it reaches physiological maturity.
Farmers, meanwhile, must choose which experts to bet on. And the stakes are high, with farmers who pick the wrong side either losing up to 10 per cent of their corn, or else paying too much in drying bills.
Purdue scientist Bob Nielson says he isn't trying to make waves. He's simply telling the world what he's seen in his plots.
That is, farmers can expect to lose one per cent of yield for every point of moisture reduction they achieve by field drying. So Ontario farmers who leave their corn in the field until it hits 25 per cent moisture will harvest five per cent fewer bushels.
Other scientists make no effort to hid their disbelief. "It's outrageous...it simply can't happen," says Thys Tollenaar, University of Guelph scientist and one of North America's foremost corn physiologists.
And Pioneer International, which paid for Nielsen's research, says it doesn't believe the results either. "It's not good science," says Steven Butzen, Pioneer agronomist based at Des Moines. "We believe it's based on a measuring problem, that's our bottom line."
Despite the criticism, Nielsen stands by his results, and is conducting more studies to find out the cause of the so-called "mystery yield loss."
The first findings came as an offshoot of a four-year (1991-94) project that Nielsen started in order to look at the consequences of late planting. As part of the study, Nielsen collected corn samples when the kernels reached physiological maturity, when a black layer at the base of each kernel prevents the corn plant from loading the grain with more carbohydrates.
In his Indiana plots, black layer formed at an average 28.4 per cent moisture. (In Ontario, black layer forms at about 31 per cent moisture.)
Nielsen continued to study grain as it field dried down to 20 per cent.
Using three hybrids, Nielsen found that dry matter yield shrank at the same rate as moisture loss. In 1991, for instance, for every point of moisture removed through field drying, the dry-weight harvest fell 1.1 per cent. In 1994 it fell 0.9 per cent, the lowest in the test.
Each of the three Pioneer hybrids suffered yield loss: 3527 fell 0.9 per cent, 3394 fell 1.0 per cent, and 3245 fell 1.3 per cent per point of moisture removed by field drying. Nielsen can't explain why. "Our current hypothesis is that respiration is at least partially responsible," Nielsen told Farm & Country. "We're conducting kernel digestion procedures in the lab to determine which fractions of the kernel are decreasing with field drydown."
Nielsen also stresses, however, that the rates of loss are remarkably consistent across years, with essentially the same losses in the warm, dry fall of 1991 as in the cool, wet harvest of 1992.
"If mature grain were allowed to dry down 10 percentage points in the field, the potential yield loss would be 10 per cent," Nielsen said. "Optimum grain moisture content for harvest is near 25 per cent."
Guelph's Tollenaar is more than doubtful. "I don't believe it [Nielsen's findings]."
Tollenaar says the whole point of the evolution of seeds has been to produce a stable segment of a plant's life cycle that can survive for years without major changes.
"If a seed loses dry matter at such a rate, it will be a very poor seed," he says.
Once a kernel forms a black layer, most life processes essentially shut down. "There could be losses due to respiration, but they will be small...very, very small." Tollenaar believes farmers should ignore Nielsen's work, at least until there's broader scientific consensus that the mystery yield loss is real.
That's the same advice that comes from Pioneer's Butzen. "We've looked at six other studies," Butzen says. "None of them support the Purdue work."
In fact, Pioneer was so surprised at the Nielsen results, the company launched its own in-house trials. First-year results with two Pioneer hybrids at two locations, harvested from black layer through to 15 per cent moisture, show absolutely no hint of dry matter loss, Butzen points out.
Butzen advises corn growers to plot their harvest strategy based on sure-fire agronomics and economics. Ideally, a harvest at about 25 per cent moisture provides the best compromise between field loss, combine damage and drying costs, Butzen says.
If corn is intended for high-quality milling markets, higher moisture can force the use of higher dryer temperatures, leading to stress cracks and the possible loss of premiums. On the other hand, if stalks are damaged by corn borers or stalk rots, leaving the crop in the field can put more ears on the ground instead of in the tank.
"We're skeptical," Butzen says. "We certainly don't believe that farmers should pay higher drying bills based on this one Purdue study."
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thoughts on drying corn
