The effectiveness of Yellow lupine (Lupinus luteus L.) green manure cropping in sand mine cast reclamation

- Soil C enrichment by green manuring with Yellow lupin facilitates reforestation of sand mines.

Yellow lupine (Lupinus luteus L.) green manure (GM) cropping is an important part of the current biological reclamation treatments used in sand mining cast reclamation in the Upper Silesia Region (southern Poland) prior to reforestation. Research on this system has been limited; however, the potential benefits of using Yellow lupine in reclamation in similar climatic and site conditions may be promising. Therefore, studies were conducted in chronosequence to determine the efficacy of treatment combinations that consisted of 1 or 2 years of lupine green manure cropping and fields left to fallow, where forest humus had been added to sandy mine soils. Surface soil (0-8 cm), subsurface soil layers (8-30 cm), and aboveground plant biomass (planted lupine and successional weeds, respectively) were collected regularly along transects in the study plots. We also counted the number of vascular plant species that grew on the fields left to fallow. Soil sample controls in the 0-30 cm layer were collected on adjacent sand fields (before reclamation) and in the stockpiled forest humus (upper forest soil layers prior to mining for topsoiling). Variables of measure included: soil texture, pH, bulk density, C, N, C-to-N ratio in the soil, and plant biomass. C and N pools in developed reclamation management (soil layers + plant biomass) and changes in chronosequence were evaluated. High C and N accumulations were observed in developed ecosystems. We found up to 13.55 Mg of C ha−1 and 2.40 Mg of N ha−1 in the soil and 15.02 Mg of C ha−1 and 2.60 Mg N ha−1 in the pools of the soil + plant biomass. The C pool in the system was highest after the first year of lupine cultivation; however the differences in the N pool were not significant in the studied chronosequence. Thus, based on the results, and with consideration of the reclamation work and time involved before reforestation, 1 year of lupine GM cropping is recommended.