A field experiment commenced in Hindiyah District, Kerbala, Iraq, during the growing season of 2022–2023, to evaluate the effect of Azotobacter and orange (Citrus sinensis L.) peel treatments on the growth and yield characteristics of fenugreek (Trigonella foenum-graecum L.). The experiment had a randomized complete block design with factorial arrangement of two factors and three replications. The first factor included four levels of the Azotobacter bacteria (control, 20, 50, and 100 g L^-1), while the second comprised four concentrations of orange peel extract as a soil amendment (control, 100, 150, and 200 g L^-1). The treatment with Azotobacter (100 g L^-1) indicated significant effects and provided the highest mean values of the compounds, quercetin, diosgenin and trigonelline (33.20, 36.57, and 37.05 mg g^-1, respectively). The results also revealed the remarkable effect of the treatment with orange peel (200 g L^-1), which gave the maximum values of the quercetin, diosgenin, and trigonelline (31.99, 35.73, and 35.91 mg g^-1, respectively). The interaction effects of the Azotobacter and orange peels were also substantial for all the traits of fenugreek (T. foenum-graecum L.) under study.

Keywords: Fenugreek (T. foenum-graecum L.), Azotobacter, orange peels, secondary compounds, growth and yield traits

Key findings: In fenugreek (T. foenum-graecum L.), the treatments with Azotobacter (100 g L^-1), orange peels (200 g L^-1), and their interactions indicated significant effects to improve the concentrations of secondary metabolism compounds and yield parameters.