Canopy closure effects on seed molybdenum content in Type II common beans

Abstract In Brazil, Type II common bean ( Phaseolus vulgaris L.) is typically sown at 40‐ to 50‐cm row spacing with 12–15 seeds m −1 . This conventional arrangement results in suboptimal interception of foliar‐applied molybdenum (Mo) used to enhance seed Mo content (SMoC). We hypothesized that a denser canopy would enhance both SMoC and yield and that this effect would be consistent across different Mo application rates. Canopy closure was manipulated by varying row spacing (25 or 50 cm) and plant density (8 or 16 plants m −1 ). Sodium molybdate was foliar‐applied at rates of either 300 or 600 g ha −1 of Mo, in split applications of 100 + 100 + 100 or 100 + 250 + 250 at the V4, R6, and R7 growth stages. Two sprinkler‐irrigated trials were conducted using a bean line partially resistant to white mold ( Sclerotinia sclerotiorum ). The data were analyzed using a linear mixed model and orthogonal contrasts. Under low white mold pressure, the average seed yield and SMoC were 4761 kg ha −1 and 3.74 µg seed −1 in 2022 and 2665 kg ha −1 and 2.52 µg seed −1 in 2023, respectively. Narrow row spacing (25 cm) increased yield by 20% versus 50 cm. At 600 g ha −1 of Mo, 25‐cm spacing increased SMoC by 12% over 50 cm, while the 50 + 16 combination increased SMoC by 18% versus 50 + 8; no differences were observed at 300 g ha −1 of Mo. Overall, our results suggest that denser canopies enhance both yield and SMoC in Type II beans, although the magnitude of the SMoC response indicates a rate dependency.