Development and Field Evaluation of a Microbially-Inoculated Feather–Straw–Lignite Compost Material for the Reclamation of Post-Mining Soils

This study addresses degraded post-mining soil reclamation by developing a novel, microbially-inoculated waste-derived feather–straw–lignite organic-mineral compost material. Formulated from chicken feathers (20%), wheat straw (60%), and lignite (20%) to optimize the initial C:N ratio, the substrate was inoculated with a multi-strain complex (MIX) of Bacillus altitudinis 33, Bacillus methylotrophicus Alk, and Streptomyces fulvissimus K59. Testing progressed from laboratory scale to a 200 dm3 dynamic reactor and a 2025 field evaluation with maize (Zea mays L.) on sandy mining soils in Konin (Poland). Inoculation accelerated maturation, yielding a favorable C:N ratio of 12.09 and stabilized NH4-N of 0.03%. Peak dehydrogenase activity reached 16 DU by day 3. Field application enhanced sandy soil properties, increasing urease activity to 3.91 UU and providing 3.4 g/kg P2O5. Consequently, maize showed a highly significant 15% increase in average shoot height (30.23 cm vs. 25.88 cm in control; t(645) = 6.63, p < 0.001) and intense green coloration. However, absolute soil enzymatic activity remained low due to early spring moisture limitations and temperature constraints typical of temperate climates. These initial findings suggest that the microbially-enriched compost shows strong potential as a safe functional soil-reclamation material and compliant alternative to synthetic fertilizers.