Effect of Salinity on Inorganic Phosphorus Fixation in Sara and Bajoa Soil Series of Ganges Tidal Floodplains

Soil salinity significantly impacts nutrient availability, especially phosphorus (P), in the southwestern regions of Bangladesh, where salinity is prevalent during the dry season. This study investigates the effect of varying salinity levels (2, 4, 8, and 12 dS m⁻¹) on phosphorus transformation and availability in two soil series, Bajoa and Sara, from the Ganges Floodplain. A laboratory incubation experiment was conducted with samples exposed to the salinity treatments over 0, 15, 30, and 60 days, followed by sequential extraction to quantify the phosphorus fractions. Results indicated that increased salinity led to a shift in phosphorus forms, with calcium-bound phosphorus (Ca-P) dominating over iron and aluminum-bound (Fe, Al-P) and reductant-soluble phosphorus (Rs-P) in both soil series. The Bajoa and Sara soils showed distinct responses, with a consistent reduction in bioavailable P as salinity levels increased. This fixation of phosphorus into less accessible forms has critical implications for nutrient management, as reduced P availability could limit crop productivity in saline soils. The study highlights the need for targeted phosphorus management strategies for saline-affected soils, emphasizing the importance of tailored fertilization practices to enhance sustainable agricultural productivity. Further research should explore adaptive management practices for phosphorus fertilization to mitigate the adverse effects of salinity on nutrient dynamics in affected regions.