Several factors can lead to a low final soybean stand. If the final population appears to be low, it is good to get an accurate estimate of the final stand count before making replant decisions. To estimate the final stand, random plants from at least ten areas of the field should be counted.
For different row spacings, plants from a specific length of row should be counted. To get the average final plant stand, the number of plants counted within a specific length of row should be multiplied by 1,000. (Table 1).
Table 1. To determine final stand, count plants in the length of row corresponding with each row spacing.
|Row Spacing (in)||Length of Row to Count Plants (1/1000th of an acre)|
In “The Best Soybean Planting Date,” data from a multistate collaboration by university Extension specialist suggest a final soybean stand count of approximately 100,000 to 135,000 plants per acre is optimum; where It is recommended to have a higher final stand of soybean in lower yield potential environments. However, soybean plants can compensate for lower than optimum populations.
Furthermore, data from the multistate collaboration suggest there is minimum downside yield risk with a final stand count from 50,000 to 75,000 plants per acre. The results from a population trial at the Dean Lee Research Station in 2020 supports this recommendation. In the 2020 population trial, there was a yield reduction for the May 6 and June 1 planting dates when the final plant stand fell below 61,000 and 67,500 plants per acre, respectively (Figures 1 and 2).
If a replant is considered when the final stand is between 50,000 to 75,000 plants per acre, the general recommendation from the multi-state collaborative research is to inter-plant a variety with a similar maturity group into the existing stand instead of starting over (Figures 3 and 4).
If considering a replant with a marginal low final stand, caution should be taken since the yield benefits from a larger population may not compensate for the lower yield potential due to a later planting date.