Soybean planting progress, emergence, and misconceptions

By Dr. Laura Lindsey, Adapted from C.O.R.N. 2022-13

Recent wet weather across the state has slowed soybean planting progress, but should be picking up with warmer and dryer weather. As of the last week of April, 2% of the soybean acres in Ohio were planted. Last year at the same time, 17% of soybean acres were planted. However, 2018 through 2020, planting progress was similar at 1-2%.

Table 1. Percent soybean acres planted in Ohio by week for the past five years (USDA NASS).

As soybean planting continues and plants emerge, here are some things to look for as well as some common misconceptions from soybean extension specialists across the U.S.

What Matters at Planting and Emergence: At this point in the growing season, obtaining a stand of sufficient plant population is the first step in ensuring maximum soybean yield. It is important to seed at a rate that will provide an adequate and relatively uniform stand. In Ohio, for soybean planted in May, we recommend a seeding rate of approximately 140,000 seeds/acre with the goal of at least 100,000 plants/acre.

Soybean Emergence Misconceptions: There are several common misconceptions about soybean emergence:

Misconception: Soybean plants need to have uniform emergence and uniform spacing aka “the picket fence” to maximize yield.

Reality: Emergence uniformity is not critically important in soybeans. Recent research has shown planter downforce did not impact grain yield regardless of tillage, soil texture or gauge wheel type. Rate of emergence over four days was altered but did not result in yield differences. Additional research has shown no difference between random drop and precision planting until seeding rates were reduced to 40,000 seeds/acre.

Misconception: Seed size of planted seed influences end of season crop yield.

Reality: Seed size can influence percent emergence (smaller seed size increased emergence 10%), but as long as an adequate stand is established, there is no influence of planted seed size on yield. Effect of seed size on emergence is dependent on soil texture, planting depth and environmental conditions from planting through emergence.

Misconception: Supplemental nitrogen is essential to maximize yield in high yield environments.

Reality: Soybeans with active nodules do not require additional nitrogen, even in high yield environments.. Yield responses to N are rare, unpredictable and not economically viable.

Misconception: Suboptimal stands (<80,000 plants/acre) call for an automatic replant.

Reality: Visual stand assessment at VE often underestimates the total number of plants that will emerge. We often ask growers and crop consultants to wait until the VC growth stage to make the call about replanting. Even at suboptimal stands, an automatic replant is not always the best economic decision penalties must be considered before replanting.

For more information on soybean emergence misconceptions, this Science for Success video featuring my colleague Dr. Michael Plumblee from Clemson University: https://www.youtube.com/watch?v=MpdokEECT5M and also this Science for Success FactSheet: https://soybeanresearchinfo.com/wp-content/uploads/2022/01/Science-for-Success-Soybean-Growth-Stages-V3.pdf

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