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Considerations for Replant Decisions in Soybean

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Publication Number: P3831
View as PDF: P3831.pdf

Replant decisions typically fall into one of three categories: (1) keep the crop as is; (2) replant it all; or (3) reduce your seeding rate, and plant into the existing stand. The decisions to keep the stand or to terminate and start over are generally the simplest. Fields with marginal stands that appear to be thin yet uniform often present more difficult decisions. Traditionally, in these situations, a supplemental planting may occur with a reduced seeding rate to bring the total plant population up to the desired level. However, little research has specifically addressed whether the added plants improve soybean yield and profitability.

Research was conducted in Mississippi to evaluate soybean yield at various stands and replanting approaches. The target seeding rate was 130,000 seeds per acre. Several removal and replant treatments were imposed to simulate marginal stands and replant methods commonly used in the field. The treatments listed in Table 1 are expressed as percentage of stand loss relative to the initial planting and replanted density.

Yield results are displayed in Figure 1. When the soybean stand was 50 percent or more of the intended population, replanting into the existing soybean did not improve grain yield compared to maintaining a reduced stand. However, when 75 percent of the initial soybean stand was lost, replanting into the existing stand improved grain yield 12 percent compared with keeping that level of reduced stand as is. This finding suggests that soybean replanting recommendations should vary depending upon the degree of stand failure. Assuming uniformity of the existing soybean, stands reduced less than 50 percent may be maintained without replanting. However, when soybean growers experience a severely reduced stand (75 percent stand loss), the best option is to retain the crop and replant additional seed to supplement the reduced stand. When stand failure is complete or the initial planting is terminated, replanting at a later date will likely reduce soybean yield potential considerably.

 

Table 1. Replant scenario and population description

Existing population description

Replant treatment

Percent stand loss from initial planting1

Percent of target population to replant2

Percent of target population achieved3

Target population achieved

None

0

0

100

Some stand loss

Reduced rate planted into existing stand

25

25

100

Some stand loss

Keep as is

25

0

75

Moderate stand loss

Reduced rate planted into existing stand

50

50

100

Moderate stand loss

Keep as is

50

0

50

Severe stand loss

Reduced rate planted into existing stand

75

75

100

Severe stand loss

Keep as is

75

0

25

Terminate failed stand

Full Replant

100

100

100

1Percent loss from targeted population following initial planting.

2Percent of targeted population to replant into existing soybean stand.

3Percent of overall targeted population achieved either with initial planting alone or between initial planting and one replant attempt.

 

Described in text and table.

Figure 1. Soybean yield observed across each population removal and replant scenario.


Publication 3831 (POD-10-22)

By Trent Irby, PhD, Associate Extension Professor, and Alanna B. Scholtes, Extension Associate III.

The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.

Department: Plant and Soil Sciences
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Authors

Portrait of Dr. Jon Trenton Irby
Associate Extension Professor
Extension Associate III