Phosphorus (P) losses through leaching increase phosphate fertilizer demand, raise crop production costs, and pose environmental risks. This study evaluated the potential of biochar to enhance P sorption and Olsen–extractable P in four Egyptian soils (sandy (SS), loamy (LS), clayey (CS), and calcareous (CaS)), compared five kinetic models (Pseudo–First–Order (PFO), Pseudo–Second–Order (PSO), Elovich, Intra–particle Diffusion, and Avrami), and assessed wheat responses to biochar amendment at 3% (w/w). A greenhouse pot experiment was conducted using biochars produced from bagasse (B), orange fruit waste (GF), olive stones (OS), and maize stalks (M) (pyrolysis at 450 °C for 4 h). Biochar generally increased P sorption, improved wheat biomass, and enhanced N, P, and K uptake. Relative improvements were greatest in sandy and loamy soils, whereas clayey soil showed the highest sorption capacity; bagasse and olive–stone biochars were especially effective in calcareous soil. Overall, the Elovich and PSO models provided the best fit, suggesting chemisorption–dominated, multi–step sorption processes, while the PFO and Intra–particle Diffusion models performed poorly. In general, biochar amendment enhanced P retention through multi–step mechanisms, which can reduce leaching losses and support more sustainable P management. These results highlight the need to match biochar feedstock to soil properties to optimize crop production. In general, biochar amendment enhanced P retention through multi–step mechanisms, which can reduce leaching losses and support more sustainable P management.