By Rasel Parvej, Assistant Professor & State Soil Fertility Specialist, LSU AgCenter
David Moseley, Assistant Professor & State Soybean Specialist
LSU AgCenter
Potassium deficiency symptoms in soybean first appear as irregular yellowing on the edges of K-deficient leaves, typically manifesting as early as the V3 vegetative stage (three trifoliolate leaves), primarily on the lower older leaves (Figure 1). In severe K-deficient soils, symptoms often appear on the upper younger leaves during the reproductive stages (Figure 2). Early-season K deficiency symptoms are relatively easy to diagnose and manage. However, many soybean fields experience K deficiency and consequent yield losses without displaying visible symptoms until the later reproductive growth stages (beginning seed, R5 to full-seed, R6).