Impacts of Gibberellic Acid (GA3) on growth and yield of green beans (Phaseolus vulgaris L.) in Northern Tanzania

Abstract

Green bean production in Tanzania ranges from 6 to 8 t/h which is far below the potential yield of 15 to 20 t/ha, which is largely caused by poor soil fertility of most of Tanzania’s land. Gibberellic acids (GAs) are naturally occurring growth-stimulating substances used to promote the growth and development of many plant species. Therefore, the study was carried out to determine the effects of Gibberellic acid growth hormone on the growth and yield of green beans at field conditions. The experiment was conducted using Randomized Complete Block Design with four replications and five treatments at TARI - Tengeru research farm from May to August 2023. Treatments were negative control, with three rates of Gibberellic acid (6.25 g/ha, 12.5 g/ha, and 18.75 g/ha) and Snow Paushak (500 ml/ha) as positive control. Data on growth and yield variables were collected at 33, 40, 47, 54, and 62 days after planting (DAP). The results showed that the application of GA₃ significantly (p<0.05) increased the leaf area index of green beans at 33 DAP.  Also, the application of GA₃ at 40, 47, and 54 DAP significantly (p<0.05) affected the plant height of green beans whereby GA₃ (18.75 g/ha) showed the highest. The highest plant fresh weight was recorded at GA₃ at 12.5 g/ha (13.39 t/ha) with the equivalent of 11.86% yield increase, followed by GA₃ at 18.75 g/ha (12.72 t/ha) with the equivalent of 6.27% yield increase. This study concluded that the use of 12.5 g/ha up to 18.75 g/ha GA₃ can be used as an alternative foliar fertilizer since it has shown a significant improvement in the yield of green beans. This will contribute to economic development and livelihood by engaging communities in the production of green beans. Further study particularly on economic aspects is recommended before upscaling of this practice.