Soil fertility and improvement of its properties depend on the fertilization process, which in turn affects the release of nutrients, especially phosphorus (P). The plant limitation to obtain an insufficient concentration of P is due to its fixation in primary and secondary minerals and/or its absorption on the organic materials surface. Finding an ideal formula or model is necessary to provide cross-validation between the experimental results and the empirical formula. In order to obtain the appropriate availability of P, a suitable natural alternative must be found that uses the available resources. This study aims to investigate the impact of acidified biochar at two levels with 5 incubated times on phosphorus and carbon mineralization kinetic, as well as some soil chemical properties. Six equations (Zero-order, first- order, second-order, Elovich, power function, and parabolic diffusion model) was used to describe variations of released phosphorus and carbon mineralization with time. The results demonstrated that using modified biochar led to soil pH decrease and increase of organic matter and cumulative P release by time progress for all treatments. The modified biochar caused a decline in the cumulative CO2 emissions. Also, the addition of biochar had an encouraging impact on the development and vegetative growth of fennel plants. The best treatment that increased fresh weight, dry weight, and NPK uptake by fennel plants was (BC2). The Zero-order kinetic and parabolic diffusion models give better results with value higher (R2). So, in order to create strategies for managing nutrients and soil carbon dioxide fluxes that contribute to climate change, it is crucial to consider the release kinetics and parameters associated with nutrient release and carbon mineralization from biochar.