Agronomic Approaches to Zinc Biofortification in Soil and Soilless Crops

Hidden hunger is a pressing global issue, affecting approximately 2 billion people who suffer from malnutrition, including zinc (Zn) deficiency. As an essential micronutrient, Zn plays a vital role in various physiological functions, such as gene expression, cell division, and immune system development. Zinc deficiency can even lead to death, primarily due to Zn deficiency-related diarrhea, pneumonia, and malaria. Zinc deficiency can be attributed to several factors, with inadequate dietary intake and a predominantly cereal-based diet being the main causes. The biofortification of food crops with Zn represents a promising solution to alleviate this persistent problem. Among the various biofortification approaches, agronomic biofortification is considered one of the most practical ways to enhance Zn content in crops and ultimately increase the consumption of bioavailable Zn through the diet. This chapter aims to discuss the major reasons behind Zn deficiency, and the factors affecting Zn plant uptake, and provide an overview of alternative Zn agronomic biofortification techniques applicable to a range of crops grown in soil-based and soilless cultivation systems. Besides increasing Zn content, in most cases, Zn agronomic biofortification has the potential to enhance Zn bioaccessibility and, subsequently, bioavailability, showing the potential of this solution to fulfill the ultimate goal of reducing Zn deficiency in both high- and low-income countries. Additional research is needed to develop new biofortification strategies or combine different approaches and increase Zn content while minimizing undesired effects on the content of other minerals or the crop yield performance. The agronomic biofortification of soil and soilless crops can be an effective short-term strategy to address Zn deficiency, but the successful implementation of this solution depends on the careful selection and optimization of the agronomic biofortification techniques for each target crop, considering environmental conditions, and resources available. Integrating agronomic biofortification with genetic biofortification approaches may offer the opportunity to increase the efficiency and long-term sustainability of Zn biofortification efforts.