Does size matter? More specifically, does corn seed size have an effect on stand and yield? A recent trial at Monsanto's Water Utilization Learning Center at Gothenburg, Neb., aims to answer that question.

"We see it a lot, and it really depends on the farmer's experience," says Mark Reiman, an agronomist at the center. "You had good luck with a certain shape of seed and size of seed at some point with a given hybrid. And you've had bad luck, maybe with that same hybrid, but a different seed size."

In a given year, corn growers may deal with multiple sizes and shapes of corn seed — even within the same hybrid. Some may place the blame on singulation issues with seeds that are too big or too small, resulting in doubles and skips. Others may claim bigger seeds imbibe too much water, or smaller seeds don't have enough carbohydrate reserves to get the corn plant started.

As a Monsanto seed agronomist in central Nebraska, Casey Cooksley has heard several reasons justifying farmers' seed size preferences. "I work with 35 farmers in Custer and Dawson counties. The majority of these farmers would prefer to have a certain seed size. They've adopted speed planters, and observed certain seed sizes plant better than others in terms of singulation," he says. "One farmer, in particular, is very analytical, and has always told me that his highest yields come from medium-to-large flat seeds."

Putting it to the test
So, last year, after Cooksley approached researchers at the learning center with the idea, they evaluated five different seed sizes and shapes, all using the same Dekalb hybrid — DKC60-67RIB — for yield and stand.

This included a medium-size, flat-shaped seed, weighing 34.5 pounds per 80,000-seed bag, a medium flat at 40 pounds, medium round weighing 43 pounds, a large flat size at 48.5 pounds, and a large round size at 59 pounds. All were planted on similar Hord silt loam soils at around 34,000 seeds per acre on April 25, 2017 — right before temperatures dropped and the region was hit with heavy snow.

"This plot was planted before that snow, so it was in the ground, and we were concerned about it to the point that we actually got all the seed repacked and ready to plant again, but it all emerged really well," Reiman says. "I think that is a testament to how well all seed sizes handled the cold stress."

Around three weeks later, the team began counting emerged plants on May 11-13, 15 and 22, 2017.

"There wasn't a lot that was noticeable, other than the smallest seed size tended to jump out of the ground the quickest in terms of the earliest stand count we did. The others were all pretty uniform " Reiman says, referring to the first stand count on May 11. "However, this might be something you would be worried about it in the cool environments like we dealt with last spring."

Insignificant yield difference
The results from the final stand counts on May 22 were similar. The largest seed size — the large round — had a slightly lower final stand count compared to the others. This may have been due to singulation issues with the planter, a result of larger seed size.

FINAL COUNT: Results from the final stand counts on May 22 showed no major differences between seed sizes and shapes. At the end of the year, there was only a slight difference in yields — from 269.5 bushels per acre with the smallest seed size to 264.7 bushels with the largest seed size.

At the end of the year, there was only a slight difference in yields, from 269.5 bushels per acre with the smallest seed size to 264.7 bushels per acre with the largest seed size. Meanwhile, there was no correlation between seed size and yield; some larger sizes yielded slightly higher than smaller sizes and vice versa.

However, it's still too early to say whether seed size has any effect on yield, and Reiman and Cooksley note the trial will continue for the 2018 growing season.

"Last year was the best test scenario we could have had. We had 40-degree soil temperatures starting out, and we went into extreme heat. If the large seed had more vigor, you would have thought that correlated into more yield at the end of the year," Cooksley says. "The idea is to show farmers if the seed size and shape you want aren't available, you can still produce the same yields, regardless of seed size."