Effect of applied B, Cu, Mn and Zn on soybean yield and micronutrient concentration

The effect of applied B, Cu, Mn and Zn on soybean seed yield and tissue micronutrient concentration was studied under different field conditions. Manganese application increased soybean seed yield on the Dragston, Myatt and Slagle fine sandy loams, but not on Rains fine sandy loam. Seed yield was not affected by applied B, Cu or Zn. Broadcast and foliar Mn applications were similarly effective in correction of Mn deficiency and, among foliar Mn applications, split application resulted a higher seed yield than single applications. Micronutrient concentration of the leaf blades, petioles and seeds was increased with the application of B, Cu, Mn and Zn. The increase in tissue B concentration was much greater than that of the other micronutrients. Broadcast Mn application resulted in a higher tissue Mn concentration than foliar Mn applications. The critical Mn concentration in leaf blades at the R1 growth stage was above the level of 13 µg/g, which is reported in the literature. It was concluded that the present calibration of the dilute HC1-H₂SO₄ extractable Mn soil test overpredicts the incidence of Mn deficiency in soybeans.