Management Effects On Lowest Pod Formation in Soybeans.

Management and environmental effects play a large role in determining the lowest pod-bearing node in soybean [Glycine max (L.) Merr.] and can negatively affect yield if these pods form below the reach of harvesting equipment.  The objective of this study was to determine the effects of various soybean management techniques on the lowest pod placement and yield distribution.  The effects of population density (186,000-806,000 plants ha^-1), cultivar maturity group (MG 0.8, 2.1, and 2.8), row spacing (25cm, 51cm, 76cm, and equidistant), tillage (row space cover; white mulch to simulate cornstalks, red mulch to investigate FR/R light effects, and no mulch), and thinning (from 434,000 to 186,000 plants ha^-1 at V1, R3, and R5) were investigated in 2008 at 2 locations in Minnesota.  We recorded lowest pod height, plant yield distribution, and total yield.  Using combined location analysis for all studies, population density was found to have a highly significant effect (P<0.0001) on the lowest pod placement when population was increased from 186,000 plants ha^-1 (11.48 cm) to 806,000 plants ha^-1 (18.55 cm).  Maturity group was found to have a significant effect (P<0.0001) on the lowest pod placement where lowest pod heights for early, mid, and late maturity groups were 11.21, 13.75 and 21.08 cm, respectively.  Row spacing and mulch did not have a significant effect on lowest pod placement.  Timing of thinning did not have a significant affect on the lowest pod height between V1 and R3 but did have a significant impact between R3 (12.32 cm) and R5 (17.6 cm).  Results from these studies indicate that lowest pod determination occurs between R3 and R5, and that the use of higher population densities and varieties with longer maturity may be an effective management tool to reduce harvesting losses.