Soybean Yield Potential when Seedling Population is Reduced by Planting Errors, Machinery Malfunctions, and Environmental Factors
January 21, 2025
TRIAL OBJECTIVE
- Soybean, which is the largest acreage crop in the midsouth, is planted Mid-February to Mid-July with a range of planting equipment.
- Unfavorable agronomic events during the planting season may cause growers to replant the crop.
- Previous work has shown soybean plants have a tremendous ability to compensate for these planting aberrations.
- The objective of this research was to follow up on previous research that showed existing soybean stands can be kept instead of replanted when certain bad circumstances occur.
RESEARCH SITE DETAILS
- All field work, tillage, and applied herbicides were per local standards.
- Asgrow® Brand soybean products planted:
- AG45XF3 Brand, 4.5 Relative Maturity, XtendFlex® and SR® Soybean
- AG49XF4 Brand, 4.9 Relative Maturity, XtendFlex® and SR® Soybean
- The study was designed as a single-replication strip plot with eight treatments.
- Plot size – 8 rows x 140 feet – 0.07 acre/plot
- The center 6 rows were machine harvested for yield calculations.
- Grain yield data were corrected to 13.5% moisture content.
- Seeding rate treatments in seeds/acre (Table 1)
- 120,000 (represented 0% stand reduction)
- 96,000 (represented 20% stand reduction if planted at 120,000 seeds/acre)
- 120,000 with 20% destroyed via herbicide on 5/6/24 (represented 96,000 or 20% reduction)
- 72,000 (represented 40% stand reduction if planted at 120,000 seeds/acre)
- 120,000 with 40% destroyed via herbicide on 5/6/24 (represented 72,000 or 40% reduction)
- 48,000 (represented 60% stand reduction if planted at 120,000 seeds/acre)
- 120,000 with 60% destroyed via herbicide on 5/6/24 (represented 48,000 or 60% reduction)
- 120,000 but the middle 2 of the 8 rows were destroyed via herbicide on 5/6/24 (represented non-uniform 79,200 plants/acre)
- Emergence was about 80% post planting.
UNDERSTANDING THE RESULTS
- The treatments were meant to represent agronomic scenarios that growers commonly experience in soybean fields, including:
- Normally emerged stands.
- Poor emergence that resulted in final populations being lower than intended.
- Stands which had relatively large missing areas that may have been caused by low areas, seedlings killed by backwater, or other factors (Figure 4).
- The stands were not diseased with Pythium, Fusarium, Rhizoctonia, or other seedling diseases. This experiment best represents a field which had poor emergence conditions post plant such as large rain events, cool temperatures, or other environmental or mechanical factors.
- It should be noted that the seeding rates are reported. Seedling establishment would likely be lower than seeding rate by about 20%. (As such, a 120,000 seeds/acre seeding rate would result in approximately 96,000 established plants/acre; 96,000 would be ≈ 76,800 established; 72,000 would be ≈ 57,600 established; and 48,000 would be ≈ 38,400 established, respectively.)
- In interpreting this data, several observations can be made, including:
- In general, both soybean products responded similarly to the various planting rates and loss of potential population (Figures 1 and 2).
- The 120,000 seeds/acre seeding rate with an estimated 96,000 established plants/acre was the highest yielding treatment (104.1 bu/acre) averaged across the two soybean products (Figure 3).
- In this trial, the uniform planting rates of 96,000 (98.6 bu/acre) and 72,000 (99.9 bu/acre) seeds/acre were able to compensate for stand reductions quite well with an average of 99.2 bu/acre compared to a yield of 104.1 bu/acre in the uniformly planted 120,000 seeds/acre treatment (Figure 3).
- The yield of the plot planted at 48,000 seeds/acre with ≈ 38,400 established plants (81.9 bu/acre) was about 20% lower than the yield of the uniformly planted 120,000 seeds/acre treatment plot (104.1 bu/acre; Figure 3).
- The yields in the plots with the destroyed areas appeared to decrease in a linear relationship to the size of the area destroyed (Figures 1, 2, and 3).
- The plots with the 2 missing rows demonstrated the soybean plants’ ability to compensate to some degree, although they were yield penalized compared to the treatments with higher planted/emerged stands. Weed control could also be a problem in plots with missing rows (Figure 4).
- All fields with reduced stands/missing rows should be candidates for aggressive weed control measures to help compensate for the missing shade (Figure 4).
- This data is complimentary to previous Bayer Crop Science Learning Center work.
KEY LEARNINGS
- None of these data should be taken as justification to intentionally plant at radically lower seeding rates. Doing so is likely to increase the replant potential for the reasons demonstrated in this dataset.
- These data show soybean plants have tremendous compensatory ability within a reasonable surviving population.
- All fields should be carefully evaluated prior to making the decision to replant. Fields (or areas of fields) with large missing areas should be given priority in the replanting process.
- In many situations, it is likely that a uniformly distributed soybean stand can be kept, instead of replanted, with minimal impact on yield potential.
- When deciding whether to replant, growers should consider planting-date yield penalties. These are well documented in data and should be factored into the decision along with the cost and time associated with replanting.
- Please contact your local Bayer and Asgrow® brand seed representative for more information.
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Always read and follow pesticide label directions, insect resistance management requirements (where applicable), and grain marketing and all other stewardship practices.
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