Agronomic Effectiveness of Zinc Sources as Micronutrient Fertilizers: A Comprehensive Review’

Zinc naturally occurs in the earth's crust as part of rocks and ore minerals. The average concentration of zinc in the lithosphere is 80 mg kg-1. While zinc is relatively immobile in soil, it is moderately mobile in plants. As a vital micronutrient for both humans and animals, zinc plays an essential role in plants as a catalytic, structural and regulatory cofactor for many enzyme reactions. It is necessary for the metabolism of carbohydrates, protein synthesis, the biosynthesis of growth hormones (particularly indoleacetic acid) and the maintenance of cell membrane integrity. Zinc deficiency is a widespread problem affecting both plants and humans in many regions of the world. To address this issue and improve plant zinc nutrition and yields, both soil and foliar zinc fertilizers have been applied. The agronomic effectiveness of Zn fertilizers has been related to the management factors such as placement, source type, seed treatment, foliar spray and biofortification that can affect the effectiveness of Zn fertilizers.