A nickel phytomining field trial using Odontarrhena chalcidica and Noccaea goesingensis on an Austrian serpentine soil.

Phytomining of nickel (Ni) is based on the cropping of Ni hyperaccumulators on Ni-rich serpentine soils. The efficiency of this approach is dependent on shoot nickel concentration and harvestable biomass. In a field experiment conducted on an Austrian serpentine site, the phytomining efficiency of the two plant species Odontarrhena chalcidica (syn. Alyssum murale) and Noccaea goesingensis was evaluated. O. chalcidica was planted in three treatments: control, sulphur application (0.46 g S kg-1 soil) and intercropping with the legume Lotus corniculatus. For N. goesingensis the treatments control, high-density planting (110 plants m-2) and intercropping were implemented. Given the experimental set-up, shoot biomass, shoot Ni concentration and thus the total amount of harvested Ni were on average higher for O. chalcidica. The highest Ni yield was achieved with O. chalcidica, reaching 55 kg Ni ha-1 in the sulphur treatment. N. goesingensis showed the maximum yield in the high-density treatment with 36 kg Ni ha-1. However, high-density planting of N. goesingensis and sulphur application to O. chalcidica plots did not significantly increase the Ni yield compared to the control. Intercropping with L. corniculatus tended to decrease the shoot biomass of both species. Planting of the hyperaccumulators led to a decrease of DTPA-extractable Ni and to an increase of soil pH, with the exception of sulphur-amended plots. Likewise, rhizosphere soil pH was higher than bulk soil values. Our data suggest that in particular O. chalcidica is suitable for Ni phytomining on the tested site. Measures to further increase the Ni yield and to optimise crop management will be evaluated in follow-up experiments.