Regional-scale, long-term modelling of Miscanthus phytomanagement with biostimulant application on Ni contaminated and geogenically enriched marginal lands in Emilia-Romagna under climate change scenarios

Phytomanagement with perennial energy crops can combine biomass production with progressive metal uptake from marginal and contaminated lands, but its large-scale performance requires long-term assessment. We evaluated Miscanthus × giganteus-based phytomanagement of contaminated and geogenically Ni-enriched soils in Emilia–Romagna (Italy), focusing on above-ground biomass (AGB) production and bioavailable Ni uptake. ARUNGRO was extended with (i) dose–response functions for humic acid-based biostimulants combined with mycorrhizae (MHS) and (ii) a soil–plant Ni mass balance describing uptake and depletion of the initial bioavailable Ni pool. The model was applied at 500-m resolution over 2850 ha under baseline conditions and two emission pathways (SSP1–RCP2.6 and SSP3–RCP8.5) from a single GCM (GFDL-ESM4). Control and MHS management were compared for AGB, Ni uptake, depletion times and costs. MHS increased mean AGB by 12.6% under SSP1–RCP2.6 and 15.5% under SSP3–RCP8.5. Regional cumulative Ni uptake was estimated to increase from approximately 3000 Mg at 15 years to 4900 Mg at 90 years, while costs ranged from 6.2 to 18.3 € kg−1 Ni. MHS had little effect on long-term cumulative Ni uptake but reduced T0.5 by approximately 7–9% and T0.95 by about 10%. These depletion indicators are conditional on the assumption that the bioavailable Ni pool is not replenished from less labile soil fractions. By coupling biostimulant dose–response functions with soil–plant Ni dynamics within a process-based energy-crop model, this study provides a regionally scalable framework for assessing biomass production and phytomanagement dynamics under heterogeneous soil and climate conditions.