Soybean Yield Compensation for Missing Plants in an Upland Field Converted from a Paddy Field

Field experiments were conducted over 2 years in the Hokuriku area to evaluate yield compensation for missing plants in soybean [Glycine max (L.) Merrill]. We deliberately removed some seedlings from a converted upland field planted with the soybean variety “Enrei”, and investigated the individual yield of plants growing near the sites with plants missing. There was an increase in yield of the plants that were grown adjacent to the sites where the plants had been removed. The sum of the yield increase of the plants on both sides of the gap compensated for only 42% of the average yield of an individual plant in the control group. The more plants that were removed in a series, the higher the yield of the plants adjacent to the gap. However, the increase in yield of the plants adjacent to the sites with a series of missing plants was still insufficient to compensate for the yield loss due to the missing plants, and the yield loss caused by removing a series of plants increased as the number of missing plants increased. Together, these results showed that soybean yield compensation is insufficient to compensate for the yield reduction resulting from missing plants. Therefore, gaps in fields resulting from water damage, defective seedling-planting machinery, or other issues decrease the yield, regardless of the number of missing plants. Field crop management strategies to retain seedlings are required to ensure good yields.