EFFECTS OF BIOCHAR PYROLYSIS TEMPERATURES ON THE PHOSPHORUS ABSORPTION CAPACITY OF ACRISOL SOIL (TAY NINH): BIOCHAR FROM QUAIL DUNG

Abstract

Phosphorus (P) is a critical macronutrient for plant growth. Previous research suggests that biochar derived from livestock waste can be an effective strategy for maintaining soil P availability. This study investigated the impact of biochar amendment on available P adsorption capacity in Happlic Acrisols of Tay Ninh Province, Vietnam. Quail dung biochars were prepared using a temperature range of 300-600 °C, with three specific pyrolysis temperatures of 300, 450, and 600 °C. A batch adsorption experiment was conducted to evaluate the effect of using biochar amendment (4% w/w) on soil P adsorption compared to a control treatment (unamended soil). Soil samples were equilibrated with varying phosphate solution concentrations at different time points to assess P adsorption capacity after adding. The effects of biochar pyrolysis temperature on soil properties and phosphate (P) adsorption were investigated. Key findings include: increased soil pH and pHpzc with increasing pyrolysis temperature of the biochar amendment. The recovery efficiency of biochar, total organic carbon (TOC), and cation exchange capacity (CEC) of the soil decreased with higher pyrolysis temperature. Adsorption data followed both Langmuir and Freundlich isotherm models, indicating different binding mechanisms for phosphate on the biochar surface. The maximum P adsorption capacity varied depending on the pyrolysis temperature. The pseudo-second-order kinetic model were fit for the P adsorption process, suggesting a chemisorption mechanism involving chemical interactions between biochar and phosphate ions. This finding aligns with the potential for biochar derived from quail dung pyrolyzed at 300 °C to serve as a viable strategy for enhancing P adsorption capacity in Happlic Acrisols of Tay Ninh Province, Vietnam.