Soybean Replant Decisions Made Easy(ish)!

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This past Monday, I received a text from a southern Wisconsin farmer (he asked for anonymity) sharing crop progress numbers from an agricultural consulting group (I don’t advertise for free, LOL). They reported that soybean planting was 4% ahead of average, while corn planting was 3% down. Interestingly, the farmer suggested that our recommendations, based on research funded by the Wisconsin Soybean Marketing Board (WSMB) and the North Central Soybean Research Program (NCSRP), advocating for early-planted soybeans, might be responsible for this difference! I’ll gladly take that blame!

Since that text, X (formerly known as Twitter) has been erupting with widespread images of soybeans beginning to crack and emerge. As farmers, agronomists and technical service providers begin to assess their 2024 soybean stands, below are a few factors our Science For Success team have compiled to help make any replant decision as easy as possible!For more detailed information regarding the factors above please see our full resource guide entitled: Soybean Plant Stands: Is Replanting Necessary?

For specific WI recommendations please see below!

  1. Get an accurate stand assessment. We are often drawn to the worst areas of fields and over-blow how bad the overall stand really is. You can go old school and use the tape or hula-hoop method or try a digital approach such as Bean Cam the WSMB funded soybean replant app!
    1. Link to the app store for iPhone and iPad
    2. Link to the app store for Android

      Bean Cam app calculations/results.

  2. An effective stand is obviously important to maximize soybean seed yield. However the downside yield risk for a sub-par stand is minimal until stands fall below 50,000 plants per acre. The synergy of early planting coupled with breeders adding 3x yield to soybean branches at low populations have effectively reduced the yield penalty for thins stands by 1/2 (Suhre et al. 2014) . Therefore we recommend the following.
    • Early planted soybean yield is maximized with stands that range from 100,000 (high yield environment) to 135,000+ (low yield environment) plants per acre.
    • When soybean stands are less than 50,000k plants per acre, inter-plant new seed with a similar maturity into the existing stand. DO NOT TEAR UP THE STAND AND START OVER.
    • When stands fall between optimal and 50,000k plants per acre Think Twice Before Replanting Soybeans! Our data shows a nominal ~2 bu yield increase in this situation. Even if you have a “free replant” guarantee the numbers don’t make economic sense. As a grower you are better off investing $$$ in an effective in-season residual herbicide to control weeds such as Palmer and waterhemp.

References:

Gaspar, A. and S.P. Conley. 2015. Responses of canopy reflectance, light interception and soybean seed yield to replanting sub-optimum stands. Crop Sci.55: 377-385. doi: 10.2135/cropsci2014.03.0200

Suhre, J.J., Weidenbenner, N., ‡Rowntree, S., Wilson, E., S., Naeve, S. Casteel, S.P. Conley, Diers, B., Esker, P., Specht, J., and Davis, V. 2014. Soybean Yield Partitioning Changes Revealed by Genetic Gain and Seeding Rate Interactions. Agron. J. 106:1631–1642.