Corn is more sensitive to population than soybeans, but there’s a sweet spot for both
When seed accounts for 20¢ of every input dollar, your pocketbook depends on nailing seeding rates in every field. When rates are too high, you waste money; when they’re too low you forfeit bushels.
“Seeding rate is a bigger factor when pushing yields higher,” says Wade Kent, field agronomist, Beck’s Hybrids. Mind the key factors that influence seeding rate to find the sweet spot.
“The first thing I look at [to determine seeding rate] is yield goals,” says Bill McDonnell, DuPont Pioneer certified services agent with Encirca. “Next, I consider hybrid/variety potential, soil type and economics.”
Yield goals vary by field and even within fields—you know where to expect high-end yields and where to manage for lower yields.
“In high-yielding situations, we push corn population and in low-yielding areas we back off,” Kent says. “In soybeans, you might consider a higher population in low-yielding environments to maximize leaf area.”
Corn hybrids can be flex or fixed ears, which affects seeding rate. Flex means the ear size is indetermi-
nate—it adds more kernel depth, rows and weight, depending on conditions. In lower populations, good weather and overall favorable conditions can prompt the ear to grow longer and add more kernels and kernel weight. Fixed ears have a set number of kernels.
“A flex ear stands lower populations much better,” McDonnell explains. “With fixed ears we want to push
When factoring in soil type and conditions, remember in good soil conditions you increase corn population and lower soybean population; in poor conditions it’s the inverse.
“In sandy soil, we want to keep corn populations low to moderate because resources, like water, are limited,” says Melissa Bell, commercial agronomist, Mycogen Seeds. “In soybeans, we base population recommendations not only on row width and branching ability but also on soil type as it impacts emergence. For example, sandy soils are not likely to crust and more of the seeds we plant will come up. However, tight clay soils are more likely to crust after rain or heat, so higher populations may be needed for adequate stands.”
If you increase population and yield, the math still might not work out in your favor. The yield increase has to be enough to justify the extra seed cost. Consult your yield history and seed supplier to maximize profit.
Calculating Seed Needs
There are few issues more frustrating than planting a field only to find out you are two bags short. Several factors can influence seed usage, but this calculator can help you estimate seed needs (check germination rates and make adjustments for live drop as necessary).