Stress vs. No Stress Evident in Corn Illustrated Plots

Lodging varies by water level, and plant population.

The final high yield plot of the Corn Illustrated plot project for ’07 was harvested last week. While data is still being analyzed, some facts stood out during walks through the field-sized plot just before harvest.

The 9 acre-block was set up so that half of it was irrigated all season, based on recommendations from a university-designed irrigation scheduling, computerized program. About a quarter of the plot was irrigated, but not until about a week after pollination. Then it received irrigation according to the same scheduler program. The last quarter of the plot wasn’t irrigated at all. The ground consists of three feet of loam (medium texture) soil over sand and gravel. The area experienced nearly 40 days of 90-degrees F or above, more than double the number for the average year in that area. However, the last majority of those came from August 1 through October 9, very late in the season.

Rows ran across each irrigation treatment. So one end, corn was lush, in the middle it showed remarkable recovery after irrigation was started, and on the far end, it struggled, especially as it ran out of moisture reserves. The area received only about 7 inches of rain from May 1 through October 15.

Dave Nanda, Corn Illustrated consultant, and Tom J. Bechman, editor of Indiana Prairie Farmer, did lodging counts on a hybrid at 32,000 and 40,000 plants per acre. Those reps were treated with Headline fungicide. They checked the same rows in each of the non-irrigated, late-irrigated, and irrigated sections.

“It was amazing how stress took it’s toll,” Nanda says. In the non-irrigated corn, lodging was about 30% for both populations. “Those plants were just ate up with anthracnose stalk rot,” he says. “The black dots and discoloring was quite evident in the stalks.”

Surprisingly, the late-irrigated corn was totally different. At 32,000 plants per acre, there was no lodging! That held under full irritation as well.

At 40,000 plants per acre, there was some lodging, but far less than in the non-irrigated plots. However, the most troubling fact were ears that had already dropped out of the husks onto the ground in the 40,000 plants per acre plot, both at late-irrigation and full irrigation. In one plot, while final numbers haven’t been tabulated, it appears that ear drop alone may have accounted for 10-12 bushels per acre of lost yield!

“It’s all about stress,” Nanda says. “Despite irrigation, temperatures were high and it was still a stressful year on these soils. As you push population, plants of today’s hybrids have trouble handling stress. One thing that can happen is that the ear shank isn’t as tough as it is on plants under less stress. We didn’t find ears dropping out of the stalk in the 32,000 side of the test, and it was the same hybrid, side-by-side.”

Stay tuned for more yield results. This Corn Illustrated on the Web feature will continue throughout the winter. Look for Corn Illustrated in the November issue of your Farm Progress magazine. The February edition will feature results of this year’s Corn Illustrated tests.

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