This study focused on the use of aqueous extracts from the microalgae Tetradesmus obliquus and Chlorella vulgaris in agriculture, specifically in the cultivation of common beans (Phaseolus vulgaris). Monocultures of both microalgae species were grown on a small scale in the laboratory to produce the extracts. The experimental design involved randomized blocks in a factorial design. Common bean seeds were treated with the aqueous extracts of T. obliquus and C. vulgaris at a dose of 3 mg kg seed–1. A control group was also included in the study. Each experimental group had four replicates. The cultivation period lasted 83 days.
Seed treatment had a remarkable impact on various agronomic indices of common bean. Seed treatments with aqueous extracts of T. obliquus and C. vulgaris increased plant height (38.82 ± 0.64 and 39.83 ± 0.82 cm, respectively), number of pods per plant (9.82 ± 0.40 and 11.65 ± 0.87, respectively), and yield (811.67 ± 34.57 and 865.32 ± 31.70 kg ha-1, respectively). The extract of C. vulgaris specifically increased the number of nodules per plant (41.42 ± 4.50) and the dry mass of nodules (70.42 ± 6.46 mg) compared to the control group. The productivity of black beans increased by 31.54% with seed treatment with T. obliquus and 40.24% with seed treatment with C. vulgaris, indicating the effectiveness of the aqueous extracts for both species.