Dose-dependent Optimization of NAA Foliar Sprays for Enhanced Morpho-Physiological Traits and Yield in Chilli cv. Kashi Ratna under Varanasi Conditions

Abstract

The study aims to evaluate the influence of foliar-applied Naphthalene Acetic Acid (NAA) on the growth, yield and quality attributes of chilli (Capsicum annuum L.) cv. Kashi Ratna. The present investigation was carried out during the winter season of 2023–24 at the Vegetable Research Farm, Department of Horticulture, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India. The experiment was laid out in a Randomized Block Design with nine treatments consisting of NAA concentrations ranging from 10, 20, 30, 40, 50, 60, 70 and 80 ppm along with control, replicated thrice. The treatments included T1 (NAA 10 ppm), T2 (NAA 20 ppm), T3 (NAA 30 ppm), T4 (NAA 40 ppm), and T5 (NAA 50 ppm), with T6-T9 representing higher concentrations and control.  Two foliar sprays were administered at 30 and 45 DAT. Significant improvements in vegetative traits were recorded under NAA treatments, with 50 ppm (T5) exhibiting the maximum plant height (74.13 cm), highest branching (9.94 branches) and greatest chlorophyll content (62.72 SPAD). Reproductive parameters also responded positively, as 60 ppm NAA (T6) induced the earliest first flowering (50.91 days) and 50% flowering (55.43 days). Yield attributes showed substantial enhancement, with T5 producing the highest number of fruits per plant (237.85), fruit weight (2.86 g), yield per plant (679.82 g), yield per plot (16.99 kg) and productivity (251.78 q ha⁻¹), representing a notable improvement over the control. Quality traits also improved markedly under NAA, as evidenced by increased ascorbic acid content (95.74 mg/100 g) and reduced fruit pH (6.31) in T5. Overall, the study demonstrates that foliar application of NAA, particularly at 50 ppm, optimizes growth, enhances reproductive efficiency, improves fruit quality and significantly increases yield under the agro-climatic conditions of Varanasi, making it a highly effective practice for chilli cultivation.