Yield and yield components responses of old and new soybean cultivars to source-sink manipulation under light enrichment

Limited information is available regarding the source-sink alterations on soybean yield under whole plant light enriched conditions. The differential responses of yield components for two old and two new cultivars were investigated. The yield sensitivity of the old cultivars to the changes in source strength and light enriched conditions was much greater than that of the two new cultivars. The yield of the new cultivars was more likely sink-limited, and source-limited for the old cultivars. The increased yield by light enrichment was in part due to an increased branch contribution. Pod number per plant was more responsive than seed number per pod. The reduction in pod number by source-sink manipulation was more severe in the old cultivars. Light enrichment increased pod number in the two old cultivars but not in the two new cultivars. Seed size was responsive to changes in the source-sink ratio and changes in the environment. Both pod number or seed size may be increased or decreased if environmental conditions for seed filling are altered.