Low soybean plant population: Is replanting necessary?

Early in the growing season, abiotic (freezing temperatures, hail, flooding, etc.) and biotic (slugs, deer, disease, insects, etc.) factors often reduce soybean [Glycine max (L.) Merr.] plant populations. Although seeing a soybean field with poor seedling vigor, slow plant growth, and low plant population density often triggers an urge to replant, such fields do not always need to be replanted. The objectives of this management guide are to (a) address the necessary considerations prior to replanting a soybean field; (b) provide images depicting common early season stressors affecting soybean; and (c) explain the potential yield limitations from early season soybean injuries. US soybean agronomists representing a diversity of growing regions collated replant guidelines to generate applicable recommendations and pictures showing effects of early-season stressors that reduce soybean plant population. The minimum soybean stand required to produce near-maximal yields has been as low as 50,000 plants per acre, but more plants than that may be required in the case of adverse growing conditions, in northern regions, or with early-maturing varieties. When the plant population is low, repair planting—adding seeds without destroying established plants—portions of the field instead of destroying the existing stand and starting over is recommended. Management in reaction to stand loss should consider the cause and type of damage and should focus on maximizing profitability.