<![CDATA[Microalgae are photosynthetic microorganisms that serve as primary producers in aquatic ecosystems and have the potential to be developed as a source of economically valuable biomass. One of the most widely cultivated microalgae is Chlorella sp. because of its rapid growth and high nutritional content. The availability of balanced nutrients in the culture medium strongly influences the successful cultivation of Chlorella sp. This study aimed to determine the effectiveness of urea, ZA, and TSP technical fertilizers at an N:P ratio of 7.2:1 in supporting Chlorella sp. productivity at the laboratory scale. The study was conducted using a Completely Randomized Design with repeated observations over time, comprising one control treatment with Dahril solution medium and five technical fertilizer combination treatments at different concentrations. The results showed that the highest cell abundance was obtained in the control treatment (K), reaching 12.54 × 10⁶ cells/mL, with a specific growth rate of 0.355 d⁻¹ and an absorbance value of 1.289. Among the technical fertilizer treatments, treatment four (P4), consisting of 203.76 mg/L ZA, 92.76 mg/L urea, and 27.48 mg/L TSP, produced the highest cell abundance, reaching 11.28 × 10⁶ cells/mL, with a specific growth rate of 0.339 d⁻¹ and an absorbance value of 1.207. The relationship between cell abundance and absorbance showed a very strong correlation, with a coefficient of determination (R²) of 0.9678. These results indicate that the combination of urea, ZA, and TSP technical fertilizers at an N:P ratio of 7.2:1, particularly in treatment P4, has the potential to serve as an alternative nutrient medium to support Chlorella sp. productivity.]]>
