Corn School: 250 Bushels or 70 Bushels — Measuring Drought Impact


How much corn yield could Ontario’s hot, dry summer cost growers?

In this episode of the Corn School, Ridgetown College, University of Guelph field crop agronomist Dave Hooker explains that drought stress can have a tremendous impact on yield, especially during the two-week period that “brackets” silking.

Hooker says that the number of rows on a cob is actually set at the V6 growth stage, and the length of the ear is determined about two weeks before silking. But what happens during the two-week silking period really determines the final kernel number and yield potential.

He compares how the same hybrid performs in drought conditions compared to a nearby plot where it received adequate moisture throughout the growing season: the plants that received rainfall are fertilized and in the blister stage while corn in the drought stricken area has green silks and is struggling through pollination.

“The silks came out much later in the stressed corn and there’s not much pollen around and there’s an excellent chance that most of these silks will not be pollinated and the corn will not be fertilized.”

Hooker says there is several ways to assess the grain yield potential of drought-impacted corn. The kernel count method requires growers to count the number of rows on the cob and then count the number of kernels per row. Multiplying these two numbers gives you the kernels per ear. Then multiply kernels per ear by the number of plants per acre. Finally, divide by the number of kernels in a bushel of corn (80,000).

Kernel count method: yield potential = number of rows × kernels per row × number of plants per acre ÷ 80,000

Based on the kernel count method, Hooker expects a huge yield difference in the hybrid featured in the video. He estimates the plants receiving adequate rainfall will yield in the neighbourhood of 250 bushels per acre, while the drought-stressed field may yield 70 bushels.

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