Widespread Zn deficiency has been found
responsible for yield reduction in rice [16].
Globally, more than 30 % of soils are low in
plant-available Zn [17]. Nonetheless, frequency
of Zn deficiency is greater in rice than other
crops, with more than 50 % of the crop worldwide
prone to this nutritional disorder [18]. Zinc
application methods and sources are aimed at
improving Zn availability for plant uptake. Zn can
be applied to soil, seed and leaves [18] and by
dipping seedlings into a fertilizer solution. Zinc
fertilization to cereal crops improves productivity
and grain Zn concentration [19,20] and thus
improves grain nutritional value for human
beings. However, the vast majority of Zn fertilizer
trials and resulting fertilizer recommendations in
rice have been in the context of managing the Zn
deficiency, with very few studies related to Zn
bio-fortification [21]. Selection of appropriate Zn
sources for soil application is considered to be an
alternative strategy to improve plant availability of
Zn under lowland conditions. Generally, ZnSO4 is
the most widely applied Zn source for its high
solubility and low cost. In addition, Zn-EDTA
(Ethylene Diamine Tetra acetic Acid) is also
being recommended due to its efficiency of Zn
availability for the plants [22].