Invasive weed‐based biochar facilitated the restoration of coal mine degraded land by modulating the enzyme activity and carbon sequestration

Abstract

Excessive growth of invasive weeds in reclaimed coal mine sites are undesirable as they compete for nutrient with the planted species. To overcome this problem, these invasive species may be converted to biochar and used as an amendment during reclamation. Objectives of the present study are to prepare biochar from invasive weeds and apply as amendment in an 8‐year‐old reclaimed mine spoil (RMS) and study the changes in spoil physio‐chemical properties, enzymatic activity, and C‐stock. Biochar was prepared at 450°C and applied at 10 t/ha (BC10) and 20 t/ha (BC20) in field condition. The result showed that biochar ameliorates RMS physio‐chemical properties significantly with respect to moisture content (+27%), available‐N (+3%), exchangeable‐K (+15%), and cation exchange capacity (+35%) in BC20 compared to control. Geometric mean of enzymatic activities index increase in BC10 (8) and BC20 (10.2) compared to control (5.8) indicating improved microbial activities. BC20 had significantly high recalcitrant carbon, which indicates higher C‐sequestration potential by biochar application. Additionally, the total C‐stock increased by 13 and 91% at BC10 and BC20, respectively. CO2 sequestered increased by 13% at BC10 and 91% at BC20 amendment. In‐situ production and surface application of biochar at 20 t/ha will cost 239 USD/ha. The study concluded that invasive weed biochar has the potential to improve the spoil nutritional properties (N & K), increase C‐stock and C‐sequestration potential in coal mine spoil.