In a year of uneven crop emergence, University of Missouri Extension agronomists say not to count out runts that emerge late. “A late-emerging corn plant is better than no corn plant,” says MU Extension agronomist Bill Wiebold.
In a weekly teleconference of MU Extension agronomists on May 7, reports varied from “no corn in the ground at all” to 40 percent planted. Regional agronomists expressed concern about uneven emergence of corn in fields already planted.
Yield loss can happen when smaller plants compete for nutrients and sunlight with larger, earlier-emerging plants. Smaller plants likely produce barren or small ears.
Seeds that emerge 10 days behind their row mates lessen in-row yield potential. Studies vary, but agronomists in Wisconsin and Illinois estimated losses at 8-10 percent in older research, says MU Extension corn specialist Greg Luce.
The numbers remain relevant, Luce says, even though improved precision-planting equipment reduces irregularities. Skips and smaller plants are still likely. “Skips are what you don’t want,” he says. “Doubles are a planter issue and certainly not desired, but they don’t have the negative impact on yield like a skip.”
Luce says uneven emergence happens for several reasons: soil crusting, compaction, inconsistent and especially shallow seeding depth and differences in soil temperature. Seed-to-soil contact matters as well. This year, cool weather provided fewer growing degree units, which are needed for corn to develop strong root systems and emerge uniformly.
“In a perfect world, we would have a picket fence and the world would look beautiful,” Wiebold says. That’s not the case in 2019, when flooding and excessive rain delayed planting and prompted early concerns of replanting.
But most uneven stands do not warrant replanting. “A ragged stand is better than no stand,” Wiebold says.
Luce agrees that replanting is not justified when only due to uneven stands.
“Although uniformity is the goal, the most important factor is the total plant population,” he says. “Too many skips and a low plant count is what calls for replanting.”
The MU Extension guide “Corn and Soybean Replant Decisions” is available for free download at extension2.missouri.edu/g4091, where you can also download MU Extension economist Ray Massey’s updated replant decision-making tool.