Assessing soybean emergence

Assessing soybean emergence will help Michigan producers detect problems early enough to make timely management decisions and take corrective measures if warranted.

Many factors can adversely affect soybean germination and emergence. Detecting and identifying emergence problems early will enable producers to make timely management decisions and implement management strategies as needed. Because of this, Michigan soybean producers should check emergence in each of their fields this spring. Under ideal conditions, soybean emergence will occur in six days, but can take more than 15 days under more challenging conditions.

There are two methods for taking soybean emergence and stand counts:

  • Counting the emerged seedlings in a length of row equal to 1/1,000 of an acre
  • Counting emerged seedlings within a well-defined sampling area (Hula Hoop method)

The Hula Hoop method is recommended for a row spacing of 10 inches or less and the 1/1,000 of an acre method is recommended for the row spacing equaling or exceeding 14 inches.

Regardless of which method you use, take 10 random samples from different areas of each field and calculate the average. This will ensure that the sampled areas and your emergence counts represent the field. Only plants that have lifted their cotyledons out of the soil should be considered as emerged.

Table 1. Length of row required to equal 1/1,000 of an acre

Row width (in inches)

Length of a single row to equal 1/1,000 of an acre

15

34 feet and 10 inches

20

26 feet and 2 inches

22

23 feet and 8 inches

28

18 feet and 8 inches

30

17 feet and 5 inches

 To use the information in Table 1 to estimate the number of soybean plants per acre in 30-inch rows, count the number of plants in 17 feet 5 inches of row at 10 random locations in the field. Simply multiply the average count for the 10 locations by 1,000 to get plants per acre. For example, if the average count in the sampled rows was 108, the population would be 108,000 emerged plants per acre.

Table 2. Converting hula hoop plant counts to plants per acre

Inside diameter of hula hoop (inches)

Conversion Factor (multiply the number of plants within the hoop by the appropriate factor to calculate plants per acre)

36

6,616

33

7,334

30

8,874

27

10,956

24

13,865

 To use the Hula Hoop method, toss the hoop in 10 random locations in the field and record the number of emerged plants within the hoop at each location. Calculate the average and multiply it by the appropriate conversion factor for the diameter of the hoop you are using. For example, if the diameter of the hoop is 30 inches and the average number of emerged plants is 16, the population is 143,984 emerged plants per acre (16 x 8,874). If the diameter of your hula hoop is not listed in Table 2, you can calculate the conversion factor with the following equation:

Conversion Factor = 43,560 ÷ [3.14 x (the inside hoop diameter in inches ÷ 2)2 ÷144]

If you count more than 100,000 plants per acre and the stand is relatively uniform, the field has the potential to produce high yields. If your emergence counts are lower than 100,000 plants per acre, you should determine the cause of the problem so that you can make informed and timely management decisions. Information on identifying and responding to soybean emergence problems is available from Michigan State University Extension.

This article was produced by the SMaRT project (Soybean Management and Research Technology). The SMaRT project was developed to help Michigan producers increase soybean yields and farm profitability. SMaRT is a partnership between MSU Extension and the Michigan Soybean Checkoff program.

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