Q/A: Questions about Soybean Emergence and Stands

Soybeans emerging in field — Digging in skips showed soybeans unable to push through hard no-till soil in this field (left). Plumule emerging from the epicotyl on a seedling that had cotyledons stripped from crusting during emergence (right). A 5% yield loss is assumed for that soybean when this happens. (Photos by Jenny Rees)

May 27, 2021

Jim Specht - Emeritus Professor of Agronomy

Q: What’s Causing Problems with My Soybean Emergence and Stands?

Row Width (inches)	Row Length Representing 1/1000th of an Acre (feet and inches)
7.5	69’ 7”
10	52’ 3”
15	34’ 10”
20	26’ 2”
30	17’ 5”
36	14’ 6”

A: What we’ve specifically seen in field situations in 2021 is generally harder soils due to lack of freeze/thaw this winter and crusting due to some hard rains/wind. Management options for helping soybeans in these situations include rainfall, irrigation and lightly running various types of equipment to scratch the soil surface. We share more in the following CropWatch article from 2019.

However, there could be other factors to consider such as PPO herbicide, seedling disease and seed corn maggot damage. To learn more about these factors, please see this article from 2020.

What to Do?

First determine the cause of emergence/stand problems by digging up plants in areas with “skips”. Examine what the plants look like. Are they kinked over with some part of the hypocotyl (portion of stem between the taproot and cotyledons) that is thickened from pushing? Did the cotyledons break off below ground? Was something eating the seed or newly germinated seed? What do the emerged plants look like? Do they look relatively healthy or do you notice any dark lesions on the hypocotyls?

Soybeans are highly resilient and can compensate for reduced stands. After determining the cause of emergence problems, it’s important to take stand counts in several parts of the field to determine what average population is in the field. Stand counts can be done by using a tape measure for 1/1000^th of an acre or hula hoop method for narrow row beans. As you assess plant stands, keep in mind that a gap in one plant row will be compensated by plants in the adjacent flanking rows. They will form extra branches to take advantage of the sunlight. Thus, single-row gaps may not be as yield-reducing as you might think, especially in narrower row spacings. There’s also an app from the University of Wisconsin called BeanCam that allows you to compare plant stands obtained with potential yield of the current and potential replant stands.

Recommendations

Check strip pattern chart — Figure 1. Pattern to consider for leaving check strips when replanting soybean. This pattern is based on obtaining two combine widths from the replant and check areas each. The full protocol can be found here. Please contact your local Extension educator if you’re interested in doing this.

A general guideline is to leave a field alone if plant populations are greater than 50,000 plants per acre, the stand is fairly uniform and the field can be kept fairly weed free. We realize that can be hard! University of Wisconsin found only a 2 bu/ac yield increase when replanting early soybeans between 50,000 and their optimum stand of 100,000-135,000 plants/acre.
For stands less than 50,000 plants per acre, plant a similar maturity into the existing stand; don’t tear out or kill an existing stand as early planted soybeans have a higher yield potential.
If you consider replanting, consider leaving some check strips and/or consider an on-farm research study using the layout pictured in Figure 1. The layout is part of the protocol found here and please contact your local Extension educator if you’re interested in this.

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Soybean Growth Stages