Soybean seed yield and composition response to stand reduction at vegetative and reproductive stages
Soybean [Glycine max (L.) Merr.] producers across the United States are confronted with significant economic losses annually from hail. Plant injury and yield loss are associated with defoliation and node or stand loss due to bruising and breaking of plant stems from the hail. The correlation of yield loss and leaf defoliation is well defined; however, limited information exists relative to whole plant loss. This research was designed to simulate severe hail injury by quantifying the influence of whole plant removal at different development stages on soybean seed yield and composition. Research was conducted near Clay Center, NE and West Lafayette, IN from 2003 to 2005. The timing of removal (V3, V6, R1, and R3.5) and the percent of plants removed (0, 25, 50, and 75%) were simultaneously studied. Seed yield decreased linearly as percent stand reduction increased at each location at all plant removal timings. The severity of yield loss differed within location and was dependent on removal timing and percent stand reduction. Soybean seed mass was nonresponsive to the various treatments except when plants were removed at R3.5. Seed oil content increased when 75% of plants were removed across all removal timings whereas seed protein response to plant removal timings was variable. Our research indicated that hail injury that leads to significant stand loss will cause yield loss as early as V3 soybean. Our data also suggest that stand loss did not have a deleterious effect on percentage oil content.