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Plant Science Today (PST)

Research Articles

Vol. 13 No. sp2 (2026): Recent Advances in Agriculture

Synergistic effects of humic acid, fulvic acid and chelated zinc and iron on growth, flowering and fruit quality of guava (Psidium guajava L.)

DOI
https://doi.org/10.14719/pst.14884
Submitted
7 April 2026
Published
30-06-2026

Abstract

A field experiment was carried out at the Research Farm of the School of Agriculture, Lovely Professional University, Phagwara, Punjab, India, in the month of February to August 2024. The study examined how foliar sprays of humic acid (HA) at 0.25 %, fulvic acid (FA) at 0.17 % and chelated zinc (Zn) and iron (Fe) at 0.2 % and 0.4 %, applied individually and in various combinations, influence the growth, flowering and fruit quality of eight-year-old guava (Psidium guajava L.) cv. Allahabad Safeda. Sixteen treatments were arranged in a randomised complete block design (RCBD) with 3 replicates. Parameters measured included plant height, stem girth, chlorophyll content, number of flowers per shoot, fruit set, fruit retention, fruit weight, fruit length and fruit diameter. The most effective treatment was the combination of HA, FA, chelated Zn (0.2 %) and chelated Fe (0.4 %), which achieved the highest values across all parameters: plant height increased by 0.256 m, stem girth by 0.240 cm, chlorophyll content by 6.847 SPAD, flowers per shoot by 17.430 %, fruit set by 85.55 %, fruit retention by 84.01 %, fruit weight by 235.95 g, fruit length by 7.25 cm and fruit diameter by 7.01 cm. The control (water spray) registered the lowest values in all aspects. A strong positive correlation (r > 0.92) among all parameters suggested that improved vegetative growth directly supported better flowering and fruit quality. The study concludes that integrating biostimulants with chelated micronutrients offers an effective and straight forward foliar fertilisation approach for guava growers.

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