Reasoning Behind Soil Fertilisation under Cotton Crops Based on the Relationship between the Sum of Exchangeable Bases (SEB) and Mineralisable Nitrogen (N-NH4+)

Contributing to improving cotton productivity by fertilising the soil in a sustainable manner. The experiment was conducted in a farming environment, with two one-hectare plots of farmland demarcated in each section. The study was conducted in 2019–2020 in the cotton-growing region of Ouangolodougou, Côte d'Ivoire. Two one-hectare plots of farmland were marked out. One plot served as a control and was fertilised solely with 15-15-15 NPK. The second plot, known as the test plot, received inputs corresponding to the predetermined recommendation using the N-NH4+ approach (Tié, 1995). This involved applying 200 kg of NPK (15-15-15), 100 kg of dolomite with 30% CaO, 50 kg of urea with 46% N and 50 kg of KCl with 60% K2O per hectare. Observations focused on plant height, number of fruiting and vegetative branches, internodes, bolls and yield. The study showed widespread potassium deficiency, as well as calcium and magnesium deficiency in some cases. Agronomic results revealed a significant improvement in growth parameters (plant hight, number of fruiting branches, internodes, bolls and yields (increased by a factor of 8 to 12) in plots fertilised according to the recommended approach. Statistical analysis confirmed the effectiveness of this adapted fertilisation, showing that the approach based on N-NH4+ and SBE diagnosis optimises the use of inputs, increases productivity and preserves soil quality. The study validates the hypothesis that rational fertilisation, based on an accurate fertility diagnosis, significantly improves cotton yields, unlike standard doses that are not tailored to specific needs. It illustrates the importance of localised and rational fertiliser management in ensuring the sustainability and competitiveness of the Ivorian cotton industry.