Response of Local Orange Seedlings Citrus sinensis L. to Foliar Application of Nano-NPK and Humic Acid and its Reflection on Vegetative Growth and Chemical Characteristics

Abstract

A private nursery located in the Al-Dujail District of Salah Al-Din Governorate hosted the experiment during the March 1st – February 28th 2023-2024 growing season. The goal was to determine how foliar application of the nano-fertilizer NPK and humic acid impacted vegetative and chemical growth characteristics of local orange seedlings, Citrus sinensis L. Uniform one-year-old seedlings with similar growth were selected as a method to decrease initial variance between experimental units and thus improve accuracy of results. This research was conducted using a two-factor factorial design and Randomized Complete Block Design (RCBD) with three replications for each treatment. The first independent factor was foliar application of the nano-fertilizer NPK 20:20:20 at three concentrations (0, 1, 1.5 g/L), while the second independent factor was foliar application of humic acid at three concentrations (0, 1.5, 2 g/L). A statistical analysis was performed using an analysis of variance table and significant difference comparison between means was done via the LSD test at a 0.05 significance level. The results are summarized below. Most vegetative growth and chemical growth traits of orange seedlings benefited from the use of nano-NPK fertilizer. The most substantial increase in growth occurred in the 1.5 g L^-1 spray application, which produced the maximum average growth rates for all of the vegetative growth traits (i.e., height, total leaf nitrogen, and leaf potassium) measured at 97.56 cm, 2.682 mg/g fresh wt, 3.92%, 1.69%, respectively. The results of this study show that the use of a humic acid spray significantly enhanced the vegetative growth traits and chemical growth traits of orange seedlings. The 2 g L^-1 spray application produced significant increases in plant height, number of branches per seedling, and total chlorophyll, nitrogen, and potassium in leaves by an average of 96.3 cm, 12.29 branches per seedling, 2.677 mg/g fresh wt., 3.56%, and 1.633%, respectively. Most of the vegetative and chemical growth markers measured for the two compounds were significantly affected by their interaction. When nano-NPK at 150 g L^-1 was mixed with humic acid at 2 g L^-1, the results produced were optimum for all vegetative and chemical growth markers as measured.