If you are walking your young soybean fields now and trying to explain what you see, you may want to look back at your records, even if it is a mental record, and recall how deep you planted seed in the field.
Soybean seed planted too deep or too shallow can play a role in what you see in terms of stand and plant size at this stage of the game.
If you planted fairly deep, soybeans have longer to go to pull the cotyledons out of the ground. As long as "deep" is reasonable, in most cases that will still happen successfully and you shouldn't see an issue. However, Shaun Casteel, Purdue University Extension soybean specialist, says that in certain conditions, planting deeper rather than shallower for soybeans can have an adverse effect.
He notes to some samples he has heard about or seen this spring where the hypocotyl was extended because the seed was planted relatively deep. When it did come above ground, the stem just below the cotyledons rotted off, dropping the cotyledons. Obviously, the seedling would die.
He attributed that phenomenon to herbicide injury. But it was aggravated by seeds needing to come a long way in the soil to emerge, meaning there was more time to imbibe herbicides. Also, cool wet conditions slowed growth and also allowed the developing seedling to sit in the soil with herbicide longer.
On the other hand, he's also heard about cases, especially in drilled fields, where a few soybeans were found on top. Soybeans left on top aren't going to grow. It's one reason many people have abandoned drills for 15-inch row planters. They're seeking more uniform depth placement.
Whether or not shallow seed becomes an issue may depend upon how many seeds are being placed at or just under the surface. If seed is just under the surface and the field is dry, it's not likely to germinate until a good rain occurs.
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