Thin soybean stands can produce surprisingly high yields

Consider this information when making soybean replant decisions.

May 29, 2019 - Author: ,

Plant stands from 80,000 seeds per acre planting rate. See side-by-side comparison pictures below of 80,000 versus 160,000 seeds per acre panting rate. All photos by Mike Staton, MSU Extension.
Plant stands from 80,000 seeds per acre planting rate. See side-by-side comparison pictures below of 80,000 versus 160,000 seeds per acre panting rate. All photos by Mike Staton, MSU Extension.

When poor soybean emergence and thin stands occur, producers are compelled to make timely and informed replant decisions. Accurately, assessing your soybean stand and diagnosing the cause of the emergence problems are the first steps in the process. Once the existing stand has been determined, use the information provided in this article to help inform replant decisions.

The final plant stands and yields of the lowest and the highest planting rates from 39 planting rate trials conducted in Michigan in 2015, 2016, 2017 and 2018 are compared in Tables 1, 2, 3 and 4, respectively. The detailed information from all the planting rate trials conducted from 2015 to 2018 is available in the 2017 and 2018 SmaRT On-farm Research Reports. Information provided in the following tables clearly shows that thin soybean stands can produce surprisingly high yields.

However, there were exceptions as yields from the 80,000 planting rate were reduced by more than 4 bushels per acre at nine of the 39 sites (23 percent of the time). Four bushels per acre is the breakeven yield loss for the 80,000 planting rate given current seed and crop prices. At three of these sites, the yield loss was more than 7 bushels per acre. It should be noted that none of the varieties planted in the trials were thin or straight-line plant types.

Table 1. Effect of low soybean planting rates on final plant stand and yield in 2015.

LocationRow widthPlanting date Target planting rate (seeds/ac)
80,000 160,000
Stand (plants per acre)Yield (bushels per acre)Stand (plants per acre)Yield (bushels per acre)

Cass 1

15”

13-May

79,100

48.9

133,100

54.5

St. Joseph 

Twin 8”

29-Apr

69,800

63.8

138,100

64.7

Tuscola 

15”

21-May

54,500

60.1

126,600

59.1

Sanilac 1

30”

21-May

63,200

52.7

138,400

53

Sanilac 2

15”

5-May

71,600

63.2

136,200

57.9

Berrien

30”

22-May

78,500

72.1

150,600

75.9

Cass 2

15”

14-May

78,300

72

150,000

72.4

Monroe

15”

9-May

51,500

38.9

105,800

49.8

Ingham

Twin 7”

13-May

79,900

46.5

180,000

47.6

Fairgrove

28”

19-May

73,300

65.8

151,300

66.6

Average

 

 

70,000

58.4

141,300

60.2

 

Table 2. Effect of low soybean planting rates on final plant stands and yield in 2016.

LocationRow widthPlanting date Target planting rate (seeds per acre)
 80,000160,000
Stand (plants per acre)Yield (bushels per acre)Stand (plants per acre)Yield (bushels per acre)

Tuscola 1

15”

19-May

66,000

67.2

128,200

71.7

Sanilac 1

22”

21-May

77,100

80.3

149,100

79

Sanilac 2

20”

7-May

59,200

75

124,900

79.3

Tuscola 2

15”

9-May

66,600

78

118,300

80.7

Tuscola 3

15”

9-May

65,000

71.9

122,600

77.7

Sanilac 3

24”

20-May

59,800

61.6

150,900

69.2

Cass

15”

23-May

75,300

75.6

142,300

74.5

Calhoun

30”

16-May

57,300

62

115,800

64.8

Barry

30”

2-Jun

59,000

55

130,000

56.8

Ionia

15”

19-May

69,900

77

128,200

80.1

Ingham

Twin 7”

25-May

79,400

53

138,200

51.4

Average

 

 

66,800

68.7

131,700

71.4

 

Table 3. Effect of low soybean planting rates on final plant stand and yield in 2017.
LocationRow widthPlanting dateTarget planting rate (seeds/ac)
80,000 160,000
Stand (plants per acre)Yield (bushels per acre)Stand (plants per acre)Yield (bushels per acre)

Sanilac 1

22”

19-May

71,200

61

123,100

62.2

Sanilac 2

20”

15-May

66,900

69

124,400

67.6

Tuscola 1

15”

23-May

65,000

50.8

117,600

52.5

Sanilac 3

30”

24-May

72,400

54.3

131,800

57.3

Sanilac 4

30”

31-May

73,000

36.8

155,400

42.9

Saginaw 1

15”

7-Jun

50,500

41.9

89,200

42.2

Saginaw 2

15”

7-Jun

44,000

43.0

92,500

47.2

Shiawassee

15”

15-May

61,600

42.5

131,300

45.8

Tuscola 2

15”

15-May

73,900

56.4

132,900

63.6

Calhoun

30”

8-May

59,600

44

109,300

46.4

Berrien

30”

22-May

69,800

64.2

126,500

65.2

Average 

 

 

64,400

51.3

121,300

53.8

Table 4. Effect of low soybean planting rates on final plant stand and yield in 2018

  

Location

  

Row width

  

Planting date

Target planting rate (seeds per acre)

80,000

 160,000

Stand (plants per acre)

Yield (bushels per acre)

Stand (plants per acre)

Yield (bushels per acre)

Tuscola

15”

May 14

64,700

66.0 b

124,200

68.5

Sanilac 1

30”

May 18

74,700

59.5

130,200

63.5

Barry 1

30”

May 8

62,800

65.3

97,900

62.5

Sanilac 2

22”

May 25

54,500

79.2

121,000

81.4

Barry 2

30”

May 8

51,500

53.9

92,300

57.7

Saginaw

30”

June 7

57,400

66.2 a

105,100

61.2

Eaton

15”

June 14

66,900

57.9 b

122,800

60.7

Average

   

61,800

64.0

113,400

65.1

Soybean agronomists have identified 100,000 plants per acre in narrow rows and 80,000 plants per acre in 28- and 30-inch rows as the minimum plant stands required to produce optimum yields. However, the information presented in the preceding tables shows that fields having plant stands of less than 80,000 plants per acre have the potential to produce high yields. I urge producers to consider this information when making soybean replant decisions. Producers should also consider the fact that soybean yields have been shown to decrease by 0.3 to 0.4 of a bushel per acre per day that planting is delayed after the first week of May when making replant decisions. 

80,000 seeds per acre 160,000 seeds per acre

Plant stands from the 80,000 seeds per acre planting rate (left/top) and the 160,000 seeds per acre planting rate (right/bottom) from the 2017 Sanilac 2 planting rate trial.

The case for keeping reduced stands becomes even stronger for fields having a history of white mold. The lower plant stands may actually produce higher yields than higher plant stands when conditions favoring the development of white mold occur (see the Sanilac 2 site in Table 1 and the Saginaw site in Table 4). The lowest planting rate increased soybean yields by 5 bushels per acre and income by $80 per acre over the highest planting rate at these locations.

MSU Extension offers additional educational resources and programs to help farmers as they deal with delayed planting seasons at https://www.canr.msu.edu/agriculture/delayed-planting-resources.

Tags: agriculture, agriculture and agribusiness, delayed planting, field crops, msu extension, organic agriculture, soybeans


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