Optimization of zinc oxide nanoparticle dosage in guava (Psidium guajava L.) for enhanced yield, nutritional quality, antioxidant activity and economic performance

Zinc (Zn) is the most deficient micronutrient among all and it also holds importance in human nutrition. The role of nanoparticles in meeting the micronutrient demands of horticultural crops is well known. In view of this, five levels of Zinc oxide nano particles (ZnONP), including a control, were used, with two varieties (i.e., VNR Bihi and Pant Prabhat), in a randomised block design replicated three times. VNR Bihi recorded significantly higher yield attributing characteristics and fruit yield compared to Pant Prabhat, whereas an opposite trend was recorded for the quality and biochemical parameters. Among all the levels of ZnONP, 150 ppm recorded the highest values of fruit yield; however, it remained statistically at par with 100 ppm. Increasing dosage to 200 ppm recorded loss in the fruit yield by 6.3 % reduction compared to 100 ppm. TSS, total sugars, ascorbic acid, total phenols, flavonoids and antioxidant activity were recorded as highest at 150 ppm, comparable to 100 ppm. The economic analysis revealed that a 100 ppm ZnONP spray can earn USD 961 ha-1 more than the control (no spray). B:C ratio (1.69) also recorded markedly highest value with 100 ppm. The study has shown that a ZnONP spray at a dosage of 100 ppm is the most optimal for guava production in India.