The Effect of Planting Date, Plant Density, and Selenium Foliar Spraying on Shallot (Allium ascalonicum L.) Production

This study aimed to evaluate the effects of planting date, plant density, and foliar Selenium (Se) application on growth, yield, and biochemical traits of Shallot (Allium hirtifolium) to identify optimal agronomic practices to improve crop performance and phytochemical composition under the environmental conditions of Khalateh Rudbar, Semnan Province, Iran. A factorial experiment with a randomized complete block design and three replications was established during the ۲۰۲۳-۲۰۲۴ growing season. Treatments included four planting dates (۱۶ October, ۱۵ November, ۱۵ December, and ۱۳ February), four plant densities (۶, ۱۰, ۱۴, and ۱۸ plants/m۲), and four levels of foliar Se application (۰, ۴, ۸, and ۱۲ mg/l as sodium selenate). Se sprays were applied four times at two-week intervals post-emergence. Growth parameters such as plant height, leaf area index, and yield components were measured. Biochemical analyses included allicin content, total phenolics, total flavonoids, antioxidant activity, and relative water content, assessed using standard laboratory methods. Data were statistically analyzed using ANOVA and mean comparisons at p < ۰.۰۵. Significant effects of planting date, plant density, and selenium foliar spraying were observed on all measured traits (p < ۰.۰۱). Early planting (۱۶ October) combined with low density (۶ plants/m۲) and high selenium concentration (۱۲ mg/l) resulted in the highest plant height (۵۷.۵ cm), bulb yield (۶.۲ kg/m), and highest accumulation of bioactive compounds including allicin (۲.۸۵ mg/g), total flavonoids (۵۴.۳ mg/g), and phenolics (۴۵.۳ mg/g). Selenium application enhanced LAI, especially between ۲۰ and ۳۵ days after planting, contributing to improved biomass production. Interaction effects indicated selenium’s role in alleviating stresses associated with late planting and higher plant density. The findings suggest that selecting an appropriate planting date and maintaining moderate plant density are crucial for maximizing shallot yield and quality. Foliar selenium application and the first planting date significantly promoted antioxidant and physiological properties. The results underline the importance of integrated crop management approaches to optimize yield and nutritional value, particularly in semi-arid agroecosystems. These findings provide valuable insights for shallot growers aiming to improve productivity and crop quality through timing, spacing, and micronutrient supplementation.

کلیدواژه ها:

Antioxidants ، Biofortification ، Phenolic component ، yield