Mitigating Cadmium Leaching and Improving Soil Fertility Through Biochar Application

ABSTRACT Numerous studies have proved the potential of biochar to decrease cadmium (Cd) availability and improve soil quality. Still, these studies repeatedly inspect a solo pyrolysis temperature or biochar application rate. The combined effects of fluctuating both the quantity of sawdust biochar and the pyrolysis temperature on soil properties, mainly in sandy loam soils, remain poorly understood. This research purposes to address this information gap by assessing how these variables interact to impact water holding capacity (WHC), nutrient retention, and Cd immobilization. Two types of sawdust biochar were prepared: 450°C for 2 h (B‐450) and 550°C for 1 h (B‐550). A factorial completely randomized design (CRD) with four replicates included a control (T1), soil with 1.25% biochar (T2), soil with 2.5% biochar (T3), and soil with 5% biochar (T4). The study examined Cd content, pH, organic matter (OM), electrical conductivity (EC), cation exchange capacity (CEC), water holding capacity (WHC) and the available nutrients. The results showed that biochar increased Cd adsorption, WHC, soil EC, organic carbon, CEC, and nutrient concentrations. Higher amounts of biochar resulted in a greater decrease in Cd, NH 4 ─N, Fe, Mn, Zn, and Cu. The Cd content in leachate from T4 dropped from 14 to 0.004 mg/L in 3 months. B‐550 showed superior effectiveness in immobilizing Cd, improving water retention (by 27%), and retaining nutrients at a biochar application rate of 5%. This study emphasizes the potentials of sawdust biochar, particularly B‐550 at a 5% application rate, for enhancing soil health, managing contamination, and sustainable agriculture.