The Relationship between the Number of Nodes and Pods in Soybean Communities

ABSTRACT Soybean Glycine max (L.) Merr. yield is often associated with the number of pods per unit area, which can be construed to suggest that the number of pod bearing structures (nodes) plays a role in determining yield. This hypothesis was tested in a 2‐yr field experiment at Lexington, KY (38° N latitude). Four cultivars that varied in relative maturity (0.7 to 5.3) and high and low populations (one cultivar) were used to create variation in nodes per square meter. The experiments were planted on 25 May 2010 and 31 May 2011 in 38‐cm rows (19 cm for the high population) and the target populations were approximately 43 (four cultivars), 26 (low population), and 78 (high) plants m −2 . Irrigation was used to minimize water stress. There were four replications of each treatment in a randomized complete block design. A 30‐cm section of bordered row was harvested at maturity to determine flower scars, pods, and nodes. The photosynthetically active radiation interception was roughly 90% or above at R1 for all treatments and there was little difference in incident solar radiation or temperature among treatments during flowering and pod set. There was a two‐fold variation in nodes per square meter in both years. Pods per square meter increased in concert with nodes per square meter up to approximately 70% of the maximum node number; above that level there was no change in pods per square meter. At low node levels, pods per square meter seems to be limited by the number of nodes, but at higher node levels there was no relationship between nodes and pods.