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The presence of acidic soil in rural areas poses difficulties for agricultural production. One factor regulating soil pH is the overuse of inorganic fertilizer. The increased use of fertilizers in soybean production not only raises sustainability concerns but also contributes to soil acidity. Therefore, the use of organic fertilizer could offer a solution for addressing both issues related to soil acidity and sustainability. The purpose of this study was to investigate the manipulation of soil pH using organic fertilizer for soybean production under acidic stress. The planting medium, consisting of a mixture of topsoil, rice husk charcoal, and organic fertilizer (in a ratio of 2:1:1), was supplemented with 0.5 g of NPK fertilizer as a basal treatment in each planting medium. To regulate the soil acidity to a pH of 4, we added FeSO4 and allowed the mixture to incubate for 30 days. The results demonstrate that the application of three types of organic fertilizers chicken manure (P1), oil palm empty bunch fertilizer (P2), and vermicompost (P3) positively impacts the growth of three soybean varieties. The findings indicate that the application of P2 organic fertilizer can increase vegetative growth almost 50% in soybeans on acidic soil, including plant height, leaf count, and root length. Meanwhile, applying P3 organic fertilizer can boost reproductive growth responses in soybeans on acidic soil, such as pod number (from around 0-4 unit to 42–51 unit), grain number (from around 0-5 unit to 88–90 unit), and grain weight (from around 0–0.37 g to 12–25 g). Organic fertilizer has the potential to regulate soil pH, promoting higher yields of soybeans under acidic stress.
Lestari et al. (Fri,) studied this question.