The importance of zinc (Zn): activates several enzymes, acts in the synthesis of proteins, acts in the synthesis of tryptophan, precursor of the hormone AIA (auxin).
It helps in the formation of grains. Zinc (Zn) deficiency causes smaller leaflets, with chlorotic areas between the veins, and these symptoms are more severe on basswood leaves. A zinc-deficient soybean crop will be yellowish-brown in color when viewed from a distance.
Maturation will be delayed and few pods will be produced. Very high applications of limestone and phosphorus reduce zinc availability and can cause zinc deficiency. Zinc deficiency is also very common in regions with low rainfall, where part of the soil layer has been removed by erosion or for leveling the land or building terraces.