Optimizing zinc foliar spray for zinc fortification and yield improvement in wheat

Aim: To investigate the field efficacy of foliar applied Zn at variable doses and time of application for enriching Zn concentration in different milling fractions of wheat grain and Zn loading capacity of different grain milling fractions. Methodology: A field experiment was carried out involving four graded Zn sprays (0.1, 0.2, 0.3, and 0.4%) with water-spray as control, applied at flowering stage of wheat crop at weekly intervals.Harvested wheat grains were pearled into nine fractions from the surface to the center using two rice polishers (JNMJ7 and JNMJ6). The rice polishers were able to separate the wheat grain fractions. Zinc concentration in the whole grain and grain fractions (layer 1 to layer 9) of wheat samples were digested with di-acid mixture and estimated on an Atomic Absorption Spectrophotometer. Results: Foliar application of Zn (0.3-0.4% Zn) at 14 or 21 days after flowering (DAF) increased Zn in whole grain by 15.3-17.0 mg kg(-1) (p < 0.05). Zn spray enhanced Zn concentration in all the grain layers i.e. 1st to 9th layers (L), albeit in endosperm layers (L-3-L-8) by a maximum of 10.8 mg kg(-1). However, Zn loading capacity differed in different fractions and was in the order L-8>L-6>L-7>L6 >= L-4 >= L-3 (p < 0.05). Interpretation: Foliar spray of Zn in wheat with optimum dose (0.3-0.4%) and time (14-21 DAF) can enhance Zn acquisition and loading to grain endosperm with a higher yield.