PJB-2019-1035
ENHANCEMENT OF ZINC CONCENTRATION AND BIOAVAILABILITY IN RICE GRAINS BY ZINC APPLICATION METHODS
Zohaib ur Rehman Bughio
Abstract
Zinc malnutrition in humans can be minimized by agronomic biofortification of cereal crops. Hence, a field experiment was executed to study the effects of Zn fertilization methods on grain yield, Zn concentrations and bioavailability in rice grains of two genotypes (NIA-Mehran and Shandar). The treatments involved control (No Zn), soil application (10 kg Zn ha-1), foliar application twice (0.3% Zn at booting, and one week after flowering), and foliar application thrice (0.3% Zn at booting, one week and two weeks after flowering). Zinc fertilization enhanced grain yield to 30%, Zn concentration in polished rice up to 3.3 times and 2.5 times in brown rice, while decreased phytic acid (PA) concentration to 40.7% over control treatment. Zinc application enhanced Zn bioavailability by lowering PA: Zn molar ratios to 79% in polished rice, 69% in brown rice, and increased total absorbed Zn (TAZ) to 4.7 times in polished rice and 3.7% in brown rice over control. Among Zn fertilization methods, the maximum enhancement in grain yield, Zn concentration and bioavailability in rice grains was recorded with foliar application thrice. The target level of Zn in polished rice for effective biofortification (28 mg kg-1), and the minimum PA: Zn molar ratio (< 18) was nearly met in brown rice with foliar fertilization (3x). The required TAZ (3 mg Zn day-1) was covered up to 53% with ingestion of brown rice and 33% with polished rice. We recommend that foliar Zn fertilization should be adopted in rice husbandry and humans should preferably consume brown rice to minimize Zn malnutrition.
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