Effects of pre- and post-transplantation humic acid biostimulant treatment and harvest date on yield quantity and quality parameters of sweet peppers (Capsicum annuum L.)

• The final yield was higher if seedlings were treated with humic acids. • Fruits of treated plants were sweeter, containing 10 % to 18 % more total sugars. • Phenolic contents varied greatly among treatments. • Luteolin-8-C-hexoside 1 was the most abundant phenolic compound in peppers. The quality of sweet pepper seedlings is of paramount importance for optimal growth and yield in terms of both quality and quantity. This study examines the impact of two commercially available humic acid-based biostimulants applied pre and post transplantation of seedlings on the growth, yield, and fruit quality of a snack-type sweet pepper, Capsicum annuum L. 'Cuccino Orange', at three key harvest dates. The results demonstrated that the application of the first biostimulant (Humic Blast) pre and post transplantation, significantly increased both yield (108.4 %) and fruit number per plant (123.9%) compared to control. Treated plants exhibited fruit with higher levels of glucose and fructose compared to untreated plants (10 to 18 %). However, other fruit parameters, such as length, width, and pericarp thickness, were not affected by the biostimulant treatments. While phenolic content varied among treatments, no consistent trend could be established, suggesting a complex interplay between humic acid application and secondary metabolite synthesis. The findings highlight the significance of selecting an optimal biostimulant application pattern. The application of biostimulants to seedlings has been demonstrated to enhance fruit growth and development, particularly when additional treatments are administered during the growing season. This has the additional benefit of improving yield. Overall, this research provides valuable insights into the optimal use of humic acid-based biostimulants in pepper production and offers practical guidance for growers seeking to maximize crop productivity.