Biostimulants (nano fertilizers, algal extract) are synthetic or natural compounds for application to seeds, plants, and soil to increase crops, particularly onion yields. These substances cause changes in vital structural processes to influence plant growth through improved tolerance to abiotic stresses and enhance seed and grain yield and quality. The presented study aims to determine if biostimulants beneficially increase onions’ vegetative growth, harvest, and quality of onions (Allium cepa L.). A randomized complete block design with three replications helped compare various rates of Nano NPK fertilization (0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 g/L Nano NPK + 0.5 g/L algae extract, 1.0 g/L mineral NPK + 0.5 g/L algae extract, 1.0 g/L mineral NPK, 1.0 g/L Nano NPK, and 0.5 g/L algae extract) with the control treatment (spraying distilled water only). The results showed as the Nano NPK + 0.5 g/L algae extract levels decreased, all studied parameters gradually declined. Foliar application of Nano NPK 1.0 g/L combined with 0.5 g/L algae recorded the highest significant effects, followed by 1.0 g/L mineral NPK + 0.5 g/L algae and 0.8 g/L Nano NPK + 0.5 g/L algae compared with the control. The highest values of bulb diameter (10.1 cm/plant), plant height (108.7 cm/plant), plant fresh weight (254.7 g/plant), and fresh yield (25.67 t/ha) emerged with foliar application of Nano NPK 1.0 g/L combined with 0.5 g/L algae, and the lowest values, obtained from the control treatment, were 4.2 cm/plant, 62.3 cm/plant, 100.23 g/plant, and 10.09 t/ha, respectively. The results suggested that using the algae extract combined with nano fertilizer treatment as a biostimulant will maximize onion growth parameters, yield production, and nutrient contents.

Keywords: Onion (Allium cepa L.), vegetative growth, nanotechnology, NPK fertilization, algae extract, nutrient content and yield

Key findings: Applying nanofertilizers in conjunction with the algae extracts’ usage as a biostimulant is crucial for maximizing the growth characteristics, yield production, and nutrient contents of onions.