Corn School: Late Emergers Struggle in Flag Test


Corn plants do indeed yield less when they emerge one day after their neighbour. What’s more, the yield gap widens even further for later emergers.

That’s the bottom line on the 2016 Real Agriculture flag test research,conducted by resident agronomist Peter Johnson. In this episode of Corn School, Johnson tells co-host Bernard Tobin that, based on his trials, plants that emerge one day after the first plants have broken the soil surface will yield 5% less; plants emerging two days late will lose 8% of their yield; and those appearing three days late will lose 14%. The news gets even worse for laggards emerging four days late – they yield almost 40% less.

Johnson notes that the research reinforces the theory that even emergence has a greater impact on yield than even plant spacing, but it also highlights the importance of proper soil conditions at planting.

Johnson explains how in the trials some plants that emerged on Day 1 actually yielded less than plants that emerged much later. “Emergence is important, but that microclimate you create around the seed really makes a big difference.” He notes that where there is poor seed-to-soil contact, plants can fall behind and loose yield as the season progresses. “There were some plants that emerged on Day 1 that fell so far behind they had no cob at all.”

Having adequate downforce on the planter to ensure seeds are planted at an even depth is just one management practice to help growers promote even emergence, says Johnson. He cautions, however, that poor soil conditions can undo even the best laid management plans.

“It’s important to get them all up on the same day, but make sure the soil is in the right condition, so the plants don’t change as they go through the growth stages. It’s not just the emergence.”

Check Part 1 & 2 of this Corn School series:

Flag Test Measures Emergence Impact

Does Emergence Really Matter?

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Corn School (view all)Season 6 (2017) Episode 28

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