Artemisia-Derived Biochar Modulates Ryegrass Growth and Micronutrient Availability in Alkaline Soil

Biochar performance in alkaline, low-fertility soil depends on feedstock, pyrolysis temperature, and application rate, yet the effects of mining-affected Artemisia biomass remain poorly characterized. Artemisia (SBC) and maize straw (BC) biochars produced at 400, 500, and 600 °C were applied at 1% or 5% (w/w) in a 40-day ryegrass pot experiment. We measured plant growth, chlorophyll, antioxidant enzyme activities, plant tissue Fe, Mn, Cu, and Zn, and soil pH, organic carbon, enzyme activities, and diethylenetriaminepentaacetic acid (DTPA)-extractable micronutrients. At 1%, SBC600 increased plant height and root length by 60.98% and 43.10%, respectively, versus the unamended control; SBC500 increased total chlorophyll by 145.71%. Under L-SBC500, DTPA-extractable Fe, Mn, Cu, and Zn were 100.26%, 80.37%, 153.01%, and 342.86% higher than in the control. The 5% rate raised soil pH to 9.53 and attenuated several plant and soil responses. Converting this locally available mining-area weed into biochar provides a waste-to-resource strategy that simultaneously manages metal-bearing biomass and reshapes the soil micronutrient profile: the Artemisia biochar was intrinsically richer in Fe, Mn, and Cu but lower in Zn than the conventional maize straw biochar, revealing a feedstock-specific nutrient signature. These short-term, concentration-based results demonstrate clear treatment-dependent benefits, although they do not yet quantify the source or transfer of elements or establish long-term environmental safety.