Optimizing extraction conditions to enhance the humification and soil remediation potential of compost-derived...

Compost tea (CT), primarily composed of dissolved organic matter derived from compost, is widely used in various environmental and agricultural applications. Nevertheless, limited information is available regarding how extraction parameters influence the quality of CT and its efficacy in soil remediation. In this study, a multi-factor orthogonal design L₁₆ (4³) was employed to investigate the effects of compost-to-water ratio (CWR), extraction time (ET), and aeration pattern (AP) on nutrient extraction and humification of CT, aiming to optimize the extraction conditions. Results showed that N, P₂O₅, and K₂O extraction efficiencies in all treatments ranged from 10 to 25 %, 10-20 %, and 50-85 %, respectively. The comprehensive humification score was in the range of 1.27-1.60. Among the three parameters, ET showed the most significant influence on CT quality. The optimal treatment for nutrient extraction was T15 (CWR 1:60, ET 48 h, and stirring), while T17 (CWR 1:30, ET 48 h, and aeration) exhibited superior performance on humification. Furthermore, the total Cd removal efficiency of T17 was 83.64 % after multiple washing cycles, which was attributed to an increased number of hydroxyl, carboxyl, and carbonyl functional groups that provided additional binding sites for Cd.