When soybeans emerge, the successful crop producer will make sure to examine their fields and evaluate soybean stands to decide when and if to replant. This involves physically walking the fields and examining the emerging plants to assess growth and development, as well as taking stand counts.
Counting soybean stands is similar to counting corn stands. Early season soybean stands counts are important to evaluate the germination and emergence of the new plants, but is not as important to yield as corn stand counts are. If stand counts are lacking, farmers should think about soybean replanting. The need for soybean replanting happens less frequently than corn, but if the emerged soybean population is significantly lower than expected, replanting or thickening up the existing stand, should be considered. Due to the soybean plant’s growth habit and reproductive capabilities, soybean can coexist at different crop development stages without an issue, so planting on an offset pattern from the original rows is usually sufficient.
1. Determine the yield potential of the current stand for the original planting date.
2. Determine the yield potential of a replanted or thickened stand at the replanted date of planting and estimated plant population.
For effect of plant density at three stages of development on soybean yield (Soybean Replant Decisions - PM 1851).
3. Compare the original yield potential with the replanted yield potential. Be sure to factor in replant costs like seed, fuel, time/labor and any additional weed control.
4. As a rule of thumb, replanting or thickening up should be considered if uniform stands are less than 75,000 plants per acre when planted prior to mid-May; or less than 50,000-60,000 plants per acre when planted late May into June.
5. Soybeans can compensate for low stands through increased branching and pod set.
6. Soybean seed treatments are often not necessary for replanted soybeans due to warmer soils at the time of planting, but consider a fungicidal seed treatment if the field is prone to seedling diseases.
7. Low or uneven soybean populations may be more susceptible to weed issues due to lack of early-season suppression from the plant canopy, so additional postemergence herbicide may be necessary.
8. Reference herbicide labels for any products already applied to the field to be certain residual products do not disallow replanting.
9. Maturity selection, seeding rate, and row spacing may all need adjustment due to the shorter timeframe to harvest and lack of competitive ability of late planted soybeans. If already planting a well-adapted soybean variety to the area, do not change maturity selection unless replanting occurs in late June, but do consider increasing seeding rate or narrowing row spacing to allow for more competition with weeds.