The aim of this study sought to determine the effect of Azotobacter and nitrogen fertilizer on the growth, yield, and accumulation of capsaicin content in fruits of two chili pepper (Capsicum annuum L.) hybrids. Carried out in the crop season of 2022–2023 at the University of Kerbala, District Husseiniya, Iraq, the experiment was in a randomized complete block design (RCBD) with a split-plot arrangement and three replicates. The study included two factors: the first factor was two chili pepper hybrids, i.e., Barbarian and Hyffa, and the second factor was eight fertilizer combinations (control, Azotobacter, urea [150 mg L⁻¹], urea [300 mg L⁻¹], urea [450 mg L⁻¹], Azotobacter + urea [150 mg L⁻¹], Azotobacter + urea [300 mg L⁻¹], and Azotobacter + urea [450 mg L⁻¹]). Results showed the Barbarian hybrid gave the highest total yield (18.12 t ha^-1) and capsaicin content in fruits (742.41 mg kg^-1) compared with the Hyffa hybrid. The fertilizer combination Azotobacter + urea (450 mg L⁻¹) also excelled other treatments in plant height (71.47 cm), the number of branches (9.50 branches plant^-1), stem diameter (2.37 cm), total yield (29.06 t ha^-1), and capsaicin content in chili fruits (820.20 mg kg^-1).

Keywords: Chili pepper (C. annuum L.), cultivars, Azotobacter, nitrogen fertilizer, growth and yield traits, capsaicin content

Key findings: In chili peppers (C. annuum L.), the hybrid Barbarian gave the maximum values in total yield and capsaicin content in fruits compared with the hybrid Hyffa. The fertilizer combination Azotobacter + urea (450 mg L⁻¹) showed the highest values for plant height, the number of main branches, stem diameter, total yield, and capsaicin content in fruits.