Big yield recipe includes lots of heavy kernels
No one in their right mind last June would have guessed farmers would harvest near-record yields in 2009. Not even someone with a crystal ball could have come up with that prediction.
Yet what was unthinkable nine months ago is now history. The proof is still sitting in grain bins on farms and in elevator terminals. Inquiring minds want to know: Where did all that corn come from?
“Not all factors that affect corn yields are negative,” says Bob Nielsen. The Nebraska native is an Extension corn specialist at Purdue University. “There are positive factors that impact yield, too. Some of them came into play during 2009.”
• Few aborted kernels and heavy kernels contribute to big yields.
• Most kernel abortion happens in blister to early milk stages.
• Cool summers usually mean longer grain-fill periods.
2 key factors
Superb grain fill during pollination depends upon putting as many kernels on each ear as possible, and making those kernels heavy. There were exceptions, but by and large, there tended to be more kernels per ear and heavier kernels in most situations in ’09, Nielsen says.
Harvesting more kernels per ear stems primarily from less kernel abortion. A longer grain-fill period tends to be desirable, he notes. It happened in ’09 as record cool July weather throttled back pollination and grain fill.
“It’s a balancing act,” Nielsen explains. “Cool weather makes for a longer grain-fill period, and that’s a plus.
“On the other hand, when it’s warmer, you get more dry matter produced per day. That’s also desirable,” he notes. “But in cases of cool summers, the longer grain-fill period seems to win out.”
What’s not a plus is stress at pollination. For example, drought stress commonly delays silk emergence and hastens onset of pollen shed. Sometimes the two do not coincide. That’s when poor kernel set can result.
Instead, cool temperatures and ample soil moisture favor prolonged, rapid silk elongation.
Check kernel set
“You’ve got to get out of your truck to assess kernel set,” Nielsen quips. “You can’t do it from the edge of the field. If you took time to walk fields last year, you likely found good kernel set.”
What you don’t want at that stage is kernel abortion, he notes. Stress even at the blister stage often leads to kernel abortion. Ears decide the conditions won’t allow them to fill as many kernels.
According to Dave Nanda, a plant breeder and crops consultant: “The goal of the plant is to make as many babies as possible. The plant wants progeny. When outside stresses tell it that it can’t handle as many progeny as it thought, it cuts back, hoping to produce as many good seeds as possible.”
Any kind of stress at the blister stage can lead to kernel abortion, Nielsen observes. Drought stress is one of the most common. Other stresses that can cause kernel abortion include severe nutrient deficiencies, severe leaf disease symptoms, leaf loss following hail and severe tunneling by European corn borers.
A pair of environmental factors also can cause abortion, Nielsen adds. Excessively warm nights during or shortly after pollination lead to more aborted kernels. Likewise, consecutive cloudy days during or shortly after pollination trigger it. Neither of those conditions were a factor in ’09.
“Once you get to the dough stage, it’s harder for the ear to abort kernels,” Nielsen explains. “Kernels may wind up small if conditions go sour, but they won’t be completely absent.”
The more starch that goes into kernels, the heavier the kernels. The heavier each kernel becomes, the better the odds for higher yields, Nielsen says.
The same factors that can abort kernels at the blister stage can affect the weight of kernels once corn reaches the early dough stage, he suggests. Besides the factors mentioned already, stalk rots and an early killing frost come into play, especially if the crop was planted late. Those two factors trimmed back yields in certain sections of corn-growing states last fall.
Otherwise, the plant creates dry matter as long as it can, and kernels grow heavy, Nielsen says. Without photosynthetic stress, the process continues. Those are the situations where fields are set up for big yields, he contends.
This article published in the March, 2010 edition of INDIANA PRAIRIE FARMER.