Optimizing Sunflower Productivity Through Combined Organic Amendments: A Sustainable Alternative to Mineral Fertilization in Tropical Soil

Tropical soils often suffer from rapid organic matter depletion and declining fertility, leading many farmers to rely heavily on mineral fertilizers. While effective in the short term, these inputs are costly, environmentally damaging, and increasingly unsustainable. This study evaluated whether combining two locally available organic amendments, cow dung compost and plantain peel biochar, could offer a more sustainable pathway to improve sunflower (Helianthus annuus) productivity in a tropical savanna soil in Dang locality, (Ngaoundere, Cameroon). A randomized complete block design with nine treatments, including unfertilized plots and varying combinations of compost and biochar, was established under field conditions. Soil, compost, and biochar were chemically characterized prior to application. Germination rate, Plant growth parameters (leaf number, and leaf area), phenological traits (days to flowering), and yield components (seed weight and yield per hectare) were monitored. Both biochar and the local soil were alkaline, while the compost was slightly acidic and exceptionally rich in organic matter. The combined application of compost and biochar significantly enhanced vegetative growth, stimulated flowering, and improved overall productivity. Amended plant with 500 g of compost combined with 20 g of biochar per plant (the most promising fertilizer) produced the highest seed yield (2.74 t/ha), markedly outperforming the control (1.90t/ha) and chemical fertilizer (2.10t/ha). These results demonstrate that combining cow dung compost and plantain peel biochar may improves sunflower yield by 44% and 30% respectively in comparison with control and NPK chemical fertilizer application, and also soil health, offering a sustainable alternative to mineral fertilizers for tropical smallholder farming systems.