Farmers who faced long rain delays this spring were faced with gut-wrenching decisions. If they couldn’t plant until late May or into June, when should they switch to earlier hybrids? If they had spotty stands, should they replant or not?
“Farming is not easy,” says Dave Nanda, a crops consultant based in Indianapolis. “My preference would have been to not switch to earlier hybrids until June 1, but the decisions can be complicated.
“Whether to replant or not is another tough choice. On one hand, if you replant you hope to get a better stand. But if it’s later in the season, as it was for most this year, you’re likely giving up yield potential. You also risk wetter corn at harvest — and even if replant seed was free from your seed company, you still incurred other costs for replanting.”
How Late Planting Affects Corn
One impact of late planting is that corn will likely catch up in maturity compared to what you would expect from the same hybrid planted at that time.
The moisture content may be higher than if you could have planted the hybrid May1, but it may not be as high in the fall as you might think if you planted it on May 31 or thereabouts. There is a phenomenon in corn that allows the plant to sense that it needs to speed up maturity. Purdue University Extension corn specialist Bob Nielsen and Ohio State University Extension corn specialist Peter Thomison discovered this phenomenon several years ago. It’s highlighted in the Purdue Corn & Soybean Field Guide.
The pair of specialists determined that the same hybrid planted May 31 will require about 200 fewer Growing Degree Days to reach black layer, or physiological maturity, than if planted May 1.
The plant catches up at different rates during the season. From planting to silking, late-planted corn needs about 1.6 fewer GDDs per day, the pair reported. The number of GDDs required after that point decreases even more. From planting to black layer, hybrids planted a month later need about 6.8 GDDs fewer to reach black layer.
Yield potential may be less, and the plants planted later may grow taller. But since they mature at a faster rate, the bottom line is that you might be able to plant a fuller-season hybrid than you expected — even if planting was delayed a month due to rain — and still see the corn mature safely before a killing frost in the fall.