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Corn quality bucks expectations

Corn quality bucks expectations

- Conventional wisdom on test weights and feed value was wrong. - Aflatoxin incidence more muted than expected. - Iowa test plots saw

EVERYONE knew that the 2012 corn crop was going to suffer several quality issues, not the least of which would be a plague of aflatoxin.

Expectations were that test weights would be down and feed value would be average, at best, as extraordinarily hot and dry conditions blanketed the nation's corn- and soybean-producing regions.

Everyone, as it turns out, was wrong.

Iowa State University professor Charles Hurburgh, director of the Iowa Grain Quality Lab in Ames, Iowa, told country elevator managers at a recent National Grain & Feed Assn. conference that when it came to predicting how the historic 2012 drought would affect corn quality, he was wrong seven out of 10 times.

"I didn't even bat 300 here with what we thought during the season," he explained, comparing predictions versus the reality of crop quality. "We thought we'd have small kernels, and we got that one right."

Beyond kernel size, however, Hurburgh and most of his contemporaries, not to mention conventional crop quality wisdom, were way off base.

With a drought-zapped crop, assumptions called for smaller test weights in a range of 50-54 lb./bu., and perhaps as small as the high-40s. To the contrary, however, Hurburgh said corn test weights in Iowa were much larger -- 54-58 lb./bu. on average, meaning that production was 8-9 bu. per acre larger than at a normal test weight.

"The reason for that, we think, is that modern hybrids, particularly biotech hybrids, are doing very well at 'committing suicide' when they need to," Hurburgh explained. "By committing suicide, I mean dumping everything from the plants, stalks and leaves into the kernel."

By so doing, the plant produced grain with test weights that exceeded expectations but with plant stalks that were more highly susceptible to falling or breaking during even moderate winds and storms.

"That's because stalk health was so poor as a consequence of the movement of nutrients into the kernel," he said.

Similarly, experts assumed that corn raised under this year's conditions would yield a lower average feed value than grain produced in an ideal weather pattern. Instead, Hurburgh noted that protein levels were considerably better than anticipated.

"The reality is that we've got some of the best proteins in years -- well above 8% on a 15% moisture basis, something we just haven't seen in quite a long time," he said.

Hurburgh said quality comparisons from Iowa State test plots from four separate strip trial tests -- featuring 20-40 hybrids per location in Adair, Black Hawk, Bremer and Palo Alto counties in Iowa -- showed that while yield was the poorest of the past four seasons, test weight, protein and density were the best of the four years (Table).

While yield was extremely good  in 2009, Hurburgh pointed out that, on the other hand, the crop was "a complete mess" in terms of moisture and grain handling.


Corn quality trends -- example



Test weight,














































Note: Four-strip trial tests of 20-40 hybrids per location in Adair, Black Hawk, Bremer and Palo Alto counties in Iowa. All data based on 15% moisture except test weight (as-is).

Source: Iowa State University.



Another key assumption that was mostly off base was that there would be a resurgence of aflatoxin in corn produced during the worst drought in 56 years.

"Just because you see the fungus doesn't mean you have aflatoxin," Hurburgh noted, pointing out that aflatoxin prevalence in 2012 was relatively muted compared with industry expectations.

The fungus that produces aflatoxin -- Aspergillus flavus -- grows on corn within a given temperature and moisture range. Generally, fungus growth occurs between temperatures of 45 degrees F and 120 degrees F at 16-30% moisture.

The moisture and temperature ranges within which the fungus produces toxin, on the other hand, are more finicky. Aflatoxin production generally occurs between 52 degrees F and 104 degrees F at 17-25% moisture.

"So, you need warm weather while the rain is coming down," Hurburgh explained. "You need a period of warm weather, and what we learned this year was that August rains, while they boosted soybean production in some cases, did not do us any favors for aflatoxin because it hung moisture a little bit longer than it otherwise would have been."

Because that ideal balance of temperature and moisture was not a frequent occurrence, aflatoxin incidence was nowhere near as widespread as the industry feared. Compared with 2011, Iowa State crop quality data indicated that only 6.1% of 396 quality samples yielded aflatoxin levels greater than 20 parts per billion, the general tolerance level beyond which the Food & Drug Administration limits feed usage.

"The statewide average was 5.3 ppb. There were some areas of the state that were higher than others, and, of course, there were some samples as high as 180 ppb, but on a blended grain basis, the averages are probably going to stay under 20 ppb," Hurburgh said. "That's a whole lot better than if that statewide average had been 19 or 20 or 21 ppb or something like that."


Report underscores corn quality

CORROBORATING the observations of Iowa State University grain quality expert Charles Hurburgh, the U.S. Grains Council (USGC) reported year-over-year improvements for the most recent corn crop across a range of quality indicators.

The council released its second annual "Corn Harvest Quality Report" in early December for which it gathered samples from the 12 states that produce 99% of U.S. corn exports.

Data indicated an average test weight of 58.8 lb./bu., an increase from the 2011 crop and more than 2 lb./bu. above the grade limit for No. 1 U.S. corn. Broken corn and foreign material levels were lower, as was the number of damaged kernels. Moisture, at 15.3%, also was lower than last year.

"Protein numbers were generally higher, starch was marginally lower and oil content was unchanged," according to USGC director of global strategies Erick Erickson.

One potential area of concern noted both in the USGC report and Hurburgh's Iowa observations was the frequency of stress cracks, indicating the relative susceptibility of corn kernels to break during handling. A 4% frequency this year was a slight increase from the 3% USGC reported in 2011.

Volume:84 Issue:52

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