Old-timers will recall the slogan 'knee-high by the Fourth' -- referring to the target height of the corn crop on Independence Day.
The thought was that if corn was knee-high by the Fourth it was developing normally, and with favorable weather the rest of the summer would produce a good crop.
Nowadays, in a normal year, most corn is shoulder-high by the Fourth. But this year the slogan may again prove accurate.
On June 20, the average height of the Illinois corn crop was only 11 inches, compared with the normal 26 inches. The most advanced corn was just 22 inches tall.
In Iowa, traditionally the No. 1 corn producer, crop statistician Bernie Janssen told UPI the corn wasn't tall enough going into the last full week in June to ask crop reporters to measure it.
Illinois statistician Jerry Clampet says 'Four feet high on Fourth of July' may be an appropriate slogan, but the height of corn by that magic date probably has little to do with how it will yield.
He offered some comparisons. In 1983, the corn was short on July 4 and the yield that fall was poor. In 1988, the corn was relatively tall on the Fourth but then the drought came and the yield was poor anyway. In 1990, the corn was short but matured to a good yield.
Two years ago, the average height of Illinois corn was 60 inches on July 4, but production was mixed. A drought reduced the size of the crop in east-central Illinois, but most of the rest of the state reported good yields.
Last year, when Illinois corn produced a record per-acre yield, corn was relatively short on the Fourth and development was behind normal, but produced a record 149 bushels per acre.
'The point to be stressed is that it becomes an interesting measurement to observe how the corn is developing and how tall it gets, but the proof is in how much corn is produced and that appears to be influenced more by how much rain we get in July,' Clampet said.
Janssen, the Iowa crop statistician, says the corn on his southeast Iowa farm is 'not even close to knee-high' but warmer weather predicted this week should help it grow.
However, he says it's an old wives' tale that corn likes hot weather.
'One reason we had such a huge crop last year is because of the cooler summer,' Janssen said. 'Whenever you put a crop under stress, it affects it somewhat. Corn doesn't like temperatures over 90 degrees, and if the mercury gets into the 100s during pollination it can kill the pollen.'
Looking back, Janssen says, in most years when corn was planted later than normal there was a larger crop. If corn is planted late, it means there was too much rain and so the moisture helped the crop later in the season.
'The major exception was in 1974 when the crop was planted late, the weather turned dry and we had an early frost. It was a disaster from start to finish,' he said.
How about the line from a song in the musical 'Oklahoma': 'The corn is as high as an elephant's eye'? That usually occurs in late July or early August.
How high is an elephant's eye?
Chicago's Lincoln Park Zoo says it's about 6 or 7 feet.
