Same Hybrid Under Different Conditions Looks Different

Same corn treated differently doesn't look similar.

Published on: Nov 10, 2008

Behavioral psychologists claim environment is as important as genetics in determining how a person develops and lives their life. Various studies of twins have been conducted to attempt to evaluate that theory.

Without planning it that way, Dave Nanda and the Corn Illustrated staff got a look at how the same hybrids planted on the same day perform under different conditions. The same pair of hybrids was used in all four Corn Illustrated plot experiments this year. The plots were located near Edinburgh, Ind.

Last year dry weather and heat nearly fired some of the plots. This year too much rain early, leading to nitrogen losses on some plots, then too little rain late kept a lid on yields. While better than last year, except for the high-yield plots, corn yields still didn't go as high as hoped.

Both hybrids in the high yield plot this year yielded 50 to 75 bushels more than they did in both the populations study and light intensity/row width study. The corn population study was planted three weeks before the other two, on May 5. However, it was on droughty soils, and there was no irrigation. So that explains the yield difference there.

The hybrids in the light intensity plot, planted the same day as the same hybrids in the high yield trial, were on similar soils, and both received far too much rain early. And while the light intensity plot was on average loam soils, not droughty soils, those plots still suffered when it turned dry in August. The high yield plot was irrigated.

The high yield plot was also treated with fungicide due to the presence of common rust. Other plots in the Corn Illustrated study weren't treated with fungicide this year. But perhaps the biggest difference was in nitrogen rate. The population trials received about 170 pounds of N per acre, with about 145 pounds side-dressed after planting. Corn in the light intensity study received about the same amount, but it was all applied before planting. Some 20 inches of rain in the next three weeks after planting apparently caused significant nitrogen losses. Many plants of both hybrids were showing nitrogen deficiency by late August in the light intensity plot, some even above the ear leaf. That's when losses due to nitrogen deficiency typically become serious, Nanda says.

Yet the high yield plots received roughly 250 pounds of N per acre, mostly side-dressed. There were few symptoms of N deficiency, even late in the season. And by mid-September, the corn in all other plots was drying up, while the same two hybrids in the high yield plot were healthy and green. In fact, there was still green leaf and stalk tissue on those hybrids when they were harvested during the last week of October.

There was a difference in moisture content of the grain, however. The high yield plot turned out moisture contents of 22 to 25% at harvest. Both the population studies and the light intensity study, harvested the same day, ran form 14 to 16% moisture, for the same hybrid! Test weights were actually higher in the population and light intensity plots. However, Nanda attributes most of that effect to how much drier the grain was in those plots. Test weights tend to be lower at higher moisture levels.

No one without a trained eye who didn't know the hybrids in the high yield study and the light intensity study would have guessed they were the same hybrids, especially not from Sept. 1 through harvest. Genetics is crucial, but environment also plays a key role, Nanda concludes.