Corn yield results from two factors: the number of ears and how much corn each ear produces, through length, girth and depth of kernel. Studies conducted by Farm Journal Field Agronomist Ken Ferrie show any hybrid’s yield can vary by 6 bu. to 12 bu. per thousand ears, depending on management.
The first step to maximizing yield is to create as perfect a stand as possible, Ferrie says. Shoot for a final ear count within 6% of what you planted. Here are some tips to help you get there:
1. A perfect stand needs a perfect seedbed.
Here are some parameters: adequate moisture at planting depth; soil temperature of 50˚F or higher; seed-to-soil contact, with no air pockets around the seed; and no residue at planting depth or in the furrow.
2. Plant by temperature, not by calendar.
Seed chilling can reduce ear count by 10% to 15%. It happens when seed lies in cold soil while it takes in water — the first 48 hours after planting. “Chilling can occur anytime soil water is 50˚F or lower, and it becomes really noticeable at 45˚F and lower,” Ferrie says. “When seed takes in warm water, the cell walls are elastic and able to swell. But with colder temperatures, cell walls tear as they expand. Some kernels will not germinate. Some will produce a shoot and no roots; others might produce roots but no spike. The most common symptom is corkscrewing of the mesocotyl, so the plant leafs out underground or emerges late.”
3. Focus on short-term weather.
“The soil temperature at planting, not later in the week, causes chilling,” Ferrie says. “That includes day and night temperatures. Check soil temperature in the morning to see if the night temperature held above 50˚F. You can avoid chilling if temperatures reach 50˚F in the morning and the forecast calls for it to stay there.
“If seed swells before temperatures drop, it won’t become chilled, but it will need warmer temperatures to germinate,” he adds. “You can plant in warm soil even if cold temperatures are coming. But don’t plant in cold soil just because warmer temperatures are predicted.”
This can make for a tough call when planting conditions are perfect but the soil is too cold.
“Your decision depends on how many acres you farm and how many acres you can plant per day — a 10% to 15% drop in ears in April might be the lesser of two evils compared to planting corn in June,” Ferrie says. “But if you want a perfect ear count, avoid seed chilling.”
4. Consider seed quality.
“Severe pericarp damage means tears in the embryo axis, and that seed may not germinate if it’s chilled,” Ferrie says. “Moderate pericarp damage means cracks in the pericarp in other parts of the seed. Cracks in the pericarp let water enter faster, increasing the risk of chilling. Round seed is most susceptible to pericarp damage; but we see it in all sizes and shapes. Seed with cracks in the pericarp performs OK in warm soil, but it might have a problem in cold, wet conditions.”
Planting in cold conditions can cause seed quality issues to multiply. Ideally, plants should emerge in a 48-hour window, within five days.
“If corn takes 30 days to emerge, seed planted spike-down will likely emerge later and produce poor ears,” Ferrie says. “It usually takes 24 to 48 hours for the mesocotyl to make a 180˚ turn and reach the surface, but in cold soil it can take 10 days or more. Seed with poor hybrid vigor and low-cold and saturated-cold germination scores will struggle in these conditions.”
5. Plant on time.
“If you can size your equipment and labor supply to plant your corn in five to seven days, you will have higher ear counts,” Ferrie says.
6. Plant at uniform depth.
Uniform seed depth helps ensure uniform temperature and moisture. It requires a level seedbed.
“Conventional tillage has the upper hand, if you don’t create a cloddy mess,” Ferrie says. “If you use vertical primary tillage in the fall, fracture soil uniformly across the width of the implement because the vertical harrow you run in the spring levels only the surface. Without full shattering, fields that look level on top will feel like speed bumps to the planter.“
In no-till, Ferrie says, level the seedbed with row cleaners.
Strip-till requires applying the right amount of down-pressure to hold the row unit in the ground. ”That will be easier if you stay centered on the strip,” he says.
7. Manage residue.
“Residue in the seed furrow can reduce ear count by 10% to 15%,” Ferrie says. “It causes poor seed/soil contact, wicks moisture away from the seed and increases the risk of seed disease.“
Residue is most likely to be a problem in continuous corn or fields with no-till soybeans planted into corn residue, Ferrie says.
Traditional cultivators and soil finishers bury residue. “If you run them 4" or 5" deep, most residue is placed below the seed; but some ears can still be lost from residue in the furrow,“ he says.
In vertical tillage, vertical harrows flip residue to the surface, so the row cleaner can move it away. “High-speed disks cause some of the toughest furrow residue issues,“ Ferrie says. “They bury residue right at the seed level, where row cleaners can’t reach it.”
New Planter Technology Can Boost Ear Count
To increase ear counts, look at your planter’s metering system, says Farm Journal Field Agronomist Ken Ferrie. “Metering systems have improved tremendously in the past 10 years. You can get good seed singulation with older planters, but it’s much more difficult.”
Will a high-speed planter boost yield? “If you already complete corn planting during the ideal window, a high-speed planter will not add yield,” Ferrie says. “But if you need 16 days to plant corn, and you can get that down to eight days, a high-speed planter is a much better investment than a new pickup.”
Bushels Per Ear
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