Effects of Varying Doses and Timing of Humic Acid Application on Growth and Flowering of Zinnia elegans

Aims: The aim of this work was to investigate the effect of humic acid, applied at different concentrations and time intervals, on the vegetative and flowering characters of Zinnia elegans.

Study Design: The experiment was designed as a complete randomized design with three replications and a total of nine treatments.

Place and Duration of Study: The experiment was conducted at the Department of Horticulture, School of Agriculture, Lovely Professional University, Phagwara, Punjab. The study was carried out over a specific duration in 2022.

Methodology: The study was conducted in a shaded area, where Zinnia elegans plants were subjected to foliar spraying of humic acid at three different concentrations (2.5, 3.5, and 5.0 mL/L) and at different intervals (10, 30 and 10 and 30 days both after transplanting) after transplanting. Various aspects of plant growth, including plant height, leaf area, root length, branching, and flowering parameters such as days to flower, blooming period, flower size, and number of flowers per plant were observed.

Results: The results showed that foliar application of humic acid at a concentration of 3.5 mL/L in 10 and 30 days after planting significantly increased plant height, leaf area, root length, branching, flower size, and number of flowers per plant. Plants treated with 3.5 mL/L of humic acid exhibited the highest values for these parameters compared to other treatments and the control (water spary). The days taken to flower were also reduced in plants treated with higher concentrations of humic acid.

Conclusion: The findings of this study indicate that foliar application of humic acid, particularly at a concentration of 3.5 mL/L in 10 and 30 days after planting, positively influenced the vegetative and flowering dimensions of Zinnia elegans.