Production dynamics of late kharif onion across diverse sowing windows: A principal component analysis-based approach for enhancing quality and economic viability

Abstract

Onion (Allium cepa L.) is an economically significant vegetable crop with persistent year-round demand. Supply constraints arise due to the limited shelf life of the rabi-season crop. To address this challenge, an experiment was conducted in eastern India using the cultivar ‘Bhima Dark Red’. The investigation aimed to identify the optimal sowing date between 15 June and 15 August 2023 to maximise yield and the benefit-cost (B : C) ratio. Results demonstrated that onion bulbs produced from latest sowing date (15 August; D5) exhibited superior bulb morphometric characteristics, including polar diameter (5.93 cm), equatorial diameter (5.55 cm) and the thinnest neck (0.86 cm). The D5 treatment produced an average bulb weight of 82.76 g, resulting in a maximum total bulb yield of 204.82 q ha-1. A strong positive relationship was observed between bulbing ratio (r = 0.78–0.99), average bulb weight (0.81–0.98), marketable bulb yield (0.78–0.92), total bulb yield (0.79–0.94), total biological yield (0.65–0.90) and harvest index (HI) (0.94–0.95) with bulb length and diameter. In the principal component analysis (PCA), also indicated strong positive associations for average bulb weight (0.219), marketable bulb yield (0.604), total bulb yield (0.595), total biological yield (0.456) and HI (0.130). Quality assessment of onion bulbs from the D5 treatment showed total soluble solids (TSS) content of 10.08 oBrix and acidity of 0.59 %. Nutrient content (nitrogen (N), phosphorus (P), potassium (K) and sulphur (S)) showed non-significant differences among sowing dates. These findings indicate that sowing on 15th August (D5) is optimal for achieving higher bulb yield and economic returns while maintaining adequate phytonutrient content under the agro-climatic conditions of eastern India.