Assessing the Effectiveness of Rotation Growing of Industrial Hemp and Alfalfa in Post-Mining Agricultural Reclamation: Using Soil Fauna as an Indicator

The reclamation of post-mining land for agricultural purposes has continued to be a big challenge. Our study concerns the use of soil microfauna (nematodes) and mesofauna (mites and springtails) as indicators of soil quality after 6 years of agricultural reclamation of a post-mining area in west–central Poland. A new method, which involves rotation growing of industrial hemp (H) and alfalfa (A) and incorporating the resulting biomass into the soil, was used to reclaim two sites (5 and 15 years after mining) representing different types of post-mining deposits (clayey and sandy). On each site, two plots were established, where each crop was grown for three years, but in a different order during the rotation cycle (3H3A and 3A3H). The results showed significant differences in the abundance and structure of the fauna communities between 3H3A and 3A3H reclamation practices, as well as between the reclaimed plots and non-reclaimed (NR) plots, where spontaneous succession proceeded. The three animal groups were more abundant in the reclaimed soil compared to the NR soil. The highest densities for nematodes were observed in the 3H3A plots and for the mesofauna in the 3A3H plots. The reclamation practices had a positive effect on groups involved in the regulation of C and N mineralisation, particularly bacterial- and hyphal-feeding nematodes and oribatid mites, and a negative effect on plant-feeding nematodes and euedaphic collembolans. The finding that most of the parameters of the studied biota had values resembling those of agricultural soils after 6 years of reclamation clearly indicates the effectiveness of the applied practices for transforming degraded land into soils that mirror soils under agricultural use.