Uneven emergence

Despite our best efforts — and often because of factors outside our control — emergence issues occasionally arise in our corn crop. Sometimes the issue is bad enough over a large enough area our decision to replant is simple. At other times, it can be a tough call.

A study by researchers from Wisconsin and Illinois dives deep into some of the factors affecting emergence looking at yield loss, stand loss, and the relative yield contribution provided by delayed plants in a complex plot design. Two different hybrids (fixed and flex) were planted at differing planting dates and delayed emergence levels of 25, 50, and 75.

As one would expect, the results are complex, but provide a nice look at what can be expected when planting is either delayed or emergence is uneven. For example, the study showed if 25 percent of the plants in the field emerged three weeks late, yields were about 90 percent of the maximum plot yield – and the exact same yield as was attained with 25 percent of the plants were missing and never did come up. This suggests that the contribution from late emerging plants doesn’t affect yield much one way or the other.

Another interesting facet of the study compared even emergence at three different planting dates (one and a half weeks between plantings), with the optimum planting date yielding five percent more than planting a week and a half later and an over ten percent yield drag when planting three weeks later. Interestingly, a week and a half delay even with varying degrees of stand loss didn’t fare a lot worse, with yield losses of six to nine percent at varying degrees of delayed planting.

The bottom line: sometimes things go awry, and we get to make a stand evaluation to determine whether to keep it or start over. If emergence delays are the issue, a delay of even up to a couple of weeks may not mean too much. Let’s just hope it doesn’t become an issue at all…

For full results, request a copy from any District Office or visit: https://store.extension.iastate.edu/product/3081 .

Alfalfa Weevil Showing Up

If you’re an alfalfa grower and have not yet scouted fields for alfalfa weevil, it’s time to do so. Larvae have been confirmed across the entirety of the Meadowlark Extension District with infestation numbers all over the board. A week of cooler weather helped slow feeding (and even resulted in some slight level of weevil mortality), but as temperatures warm, feeding will resume. If stands are thin or growing slowly, damage can quickly become severe.

For additional information on weevil levels, drop me a line at dhallaue@ksu.edu or contact any of our District Office.

David Hallauer50 Posts

David Hallauer is the Meadowlark Extension District agent in the areas of horticulture and crops and soils.

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