Do you sigh with relief once corn is pollinated, thinking your role in managing the crop is done? Perhaps you have time for a fishing trip before prepping the combine for harvest. Then again, maybe not!
Dan Quinn, Purdue Extension corn specialist, says assuming yield can no longer be affected through environmental shifts and management once grain fill begins may be the biggest myth of all.
“Grain fill is all about kernels filling with starch and becoming as big and heavy as possible,” he says. “We’ve proven over the past few seasons that continuing to manage the crop, making decisions such as spraying a fungicide, if necessary, can extend grain fill, resulting in heavier kernels and more yield.”
Mark Jeschke, agronomy manager for Pioneer, Johnston, Iowa, agrees that kernel weight, determined during grain fill, is tied to yield. He notes that kernel weight and test weight are two different things.
Jeschke and Pioneer staff, including Liam Bracken, Paul Hermans and James D’Aoust, carried out a field study in 2023 to evaluate if corn kernel weights varied between hybrids, and if factors such as plant population could impact final kernel weight.
“A better understanding of kernel weights and what causes them to vary can help in calculating more accurate yield estimates, too,” Jeschke says.
Facts vs. myths
Here are basic facts and myths about yield and kernel weight. Explanations are based upon findings by Jeschke and Quinn.
Fact: Genetic improvements in kernel weight over time contribute to higher yields. “Corn breeders have improved the genetic ability of hybrids to maintain kernels per ear at higher populations,” Jeschke says. “At the same time, genetic improvements in kernel weight have been associated with an extended kernel fill period.”
Myth: Kernel weight correlates well with test weight. Not so, Jeschke says. Data from the 2023 Pioneer kernel weight study at nine locations in eastern Ontario, Canada, proves the point. “Results showed that high kernel weight does not necessarily correlate to higher test weight,” Jeschke says.
In fact, the hybrid with the second-highest kernel weight posted the lowest test weight of all five hybrids in the comparison.
Fact: Extending grain fill before senescence increases kernel weight. Quinn and his crew documented this in both 2022 and 2023, two very different years. By extending grain fill through management by three to five days, they increased kernel weight around 10% and yields by 10 to 20 bushels per acre.
Myth: Yield is fully determined once corn dents — vacation time! Not even close, Quinn emphasizes. As noted in the Purdue Corn and Soybean Field Guide, kernel moisture at the beginning of R5 is about 60%, and dry matter is only 45% of final total dry matter. Black layer is still over 30 days away, and final yield can be affected, plus or minus, by 30%.
Fact: Kernel weight may decrease as plant population increases. This trend was observed in the Pioneer study. However, yield still increased as plant population increased. Jeschke notes it was a favorable growing season, producing higher-than-average kernel weights and yields.
Myth: All hybrids react the same to population increases. Not true. The Pioneer team saw differences in both the size of yield increase and shift in kernel weight between hybrids as populations increased.