Liming and soil texture affect the miscible displacement of phosphorus from organic and mineral sources in tropical oxisols

Phosphorus (P) movement in soils is influenced by flow velocities, diffusion rates, and several soil characteristics and properties. In acidic soils, P is tightly bound to soil particles, reducing its availability to plants. Organomineral fertilizers combine organic matter with mineral nutrients, enhancing P fertilization efficiency, and reducing environmental impacts. In this study, we aimed to investigate the P miscible displacement and availability in sandy loam and clayey Oxisols, focusing on the influence of soil pH and phosphorus sources (organomineral and triple superphosphate). An experimental column setup was employed to investigate P transport and sorption in both soils at their natural pH of 4.8 and an adjusted pH of 6.0. Breakthrough curves (BTCs) were used to provide insights into P transport mechanisms. Soil pH adjustment from 4.8 to 6.0 resulted in decreases in sorption coefficients and maximum P sorption capacity, highlighting the critical role of pH in P dynamics. The soil bulk density increased at the higher pH level indicated changes in soil particle arrangement, which are probably due to changes in structural stability promoted by liming and organic matter addition. Conversely, clayey soil had remarkable stability across the pH range due to the buffering properties of clay particles. The data from the BTCs were fitted by the two-site kinetic model at a pH of 4.8 and the linear model at pH of 6.0. These findings underscore the complex interactions among soil pH, texture, and mineralogical composition in regulating P dynamics. Furthermore, the study also highlights the necessity for differentiated soil management practices that incorporate these factors in order to achieve sustainable agricultural productivity and environmental protection.