Responses of Canopy Reflectance, Light Interception, and Soybean Seed Yield to Replanting Suboptimal Stands

ABSTRACT Soybean [Glycine max (L.) Merr.] planting date trends have steadily shifted earlier within the northern Corn Belt, while inclement weather, insect pressure, and disease pressure associated with spring planting can result in replanting some years. However, limited published literature exists about soybean replant thresholds for suboptimal plant stands and the effects of seed treatments on this decision. This study evaluated three planting dates, three seed treatments, and twelve seeding rate–replant combinations to determine replant thresholds in terms of maximizing seed yield, the effects of seed treatments on these thresholds, and the relationship of cumulative intercepted photosynthetically active radiation (CIPAR) and cumulative normalized difference vegetative index (CumNDVI) on seed yield. Trials were conducted during 2012 and 2013 in southern Wisconsin. Soybean planting in early May increased seed yield by 358 kg ha−1 compared with late May and by 805 kg ha−1 compared with mid‐June. Seed yield reductions were due to decreased seeds m−2 while CIPAR and CumNDVI measurements may partially explain this planting date effect. When initial plant stands were below threshold (