In the tropical acidic soils of Gagnoa, Côte d’Ivoire, rice cultivation is hindered by phosphorus immobilization due to iron and aluminum oxides. Phosphate amendments, such as phosphate rock (RP) and triple superphosphate (TSP), are used to improve phosphorus availability but can remobilize iron, particularly in temporarily flooded lowland rice fields. This study evaluates the effect of eight phosphate amendment formulations on iron dynamics in acidic rice soils. Tested on five plots over three crop cycles, the formulations showed a significant reduction in leaf yellowing symptoms and brown spots, with a decrease of 50% in yellowed leaves and 43 to 67.6% in brown spots compared to unamended plots. Additionally, grain and straw yields increased due to reduced infertile tillers and panicle sterility. Regarding iron dynamics, the amendments reduced soluble, exchangeable, acid-soluble, and bioavailable iron fractions, leading to better yields and reduced iron toxicity. TSP, with its rapid solubility, proved effective in the short term, but its effects diminished over time. In contrast, RP, with its slow phosphorus release, maintained stable yields and reduced toxicity symptoms. These results highlight the importance of choosing the appropriate phosphorus form based on soil conditions to optimize long-term rice productivity.

Soil nutrient analysis is crucial for understanding the dynamics of agricultural fertility and productivity. Phosphorus (P) stands out among soil nutrients for its fundamental role in vital biological processes such as photosynthesis, respiration, and cell division. The study of variations in phosphorus content along toposequences, according to the specific topography of the lowlands, is proving to be a relevant approach to elucidate the complex interactions between abiotic factors and biogeochemical dynamics that govern soil fertility. This study aims to characterize spatial variations in soil assimilable phosphorus (P2O5) content as a function of edaphic parameters, using a multidimensional approach along the longitudinal and transverse axes of the lowland. This study was carried out in the locality of N’Zoupouri, in the department of Botro, about 40 km from Bouaké, in the Gbêkê region of central Côte d’Ivoire. The physicochemical analyses of the soil samples were carried out by French and international standard methods. The BORUTA algorithm used in this study can select the truly significant characteristics while ranking their importance. The result shows that potassium (K) content is a determining factor directly influencing this essential nutrient’s spatial variations and temporal changes. The close relationship between potassium and phosphorus in the soil highlights the importance of optimized agronomic management, in which potassium not only plays a supporting role but also acts as a key element in the release and stabilization of phosphorus that is available to plants.