Zinc biofortification of cereals-role of phosphorus and other impediments in alkaline calcareous soils

Abstract

Alkaline calcareous soils are deficient in plant nutrients; in particular, phosphorus (P) and zinc (Zn) are least available; their inorganic fertilizers are generally applied to meet the demand of crops. The applied nutrients react with soil constituents as well as with each other, resulting in lower plant uptake. Phosphorus availability is usually deterred due to lime content, while Zn availability is largely linked with alkalinity of the soil. The present manuscript critically discusses the factors associated with physicochemical properties of soil and other interactions in soil-plant system which contribute to the nutrients supply from soil, and affect productivity and quality attributes of cereals. Appropriate measures may possibly lessen the severity of nutritional disorder in cereal and optimize P and Zn concentrations in grain. Foliar Zn spray is found to escape most of the soil reactions; thus, Zn bioavailability is higher either through increase in grain Zn or through decrease in phytate content. The reactivity of nutrients prior to its uptake is deemed as major impediments in Zn biofortification of cereals. The article addresses physiological limitation of plants to accumulate grain Zn and the ways to achieve biofortification in cereals, while molecular mechanism explains how it affects nutritional quality of cereals. Moreover, it highlights the desirable measures for enhancing Zn bioavailability, e.g., manipulation of genetic makeup for efficient nutrient uptake/translocation, and also elucidates agronomic measures that help facilitate Zn supply in soil for plant accumulation.

Keywords: Calcareous soil; Phytate-to-Zn ratio; Plant genetic makeup; Soil pH; Zinc fortification.