Influence of subsoil and soil volume on the accumulation of nickel by Odontarrhena corsica grown on a serpentine soil.

Odontarrhena corsica was grown for three months on Chrome loam topsoil and subsoil from near Reisterstown, MD, to examine the effects of varying soil masses (2.8 and 5.6 kg pot -1 ) and soil layers (topsoil vs. subsoil) on plant growth and Ni accumulation. The subsoil position effect was simulated by placing a pot of topsoil on top of a pot filled with subsoil. Shoot Ni concentrations were similar for all treatments at 7 g Ni kg -1 . Shoot yield was significantly higher in the 5.6 kg treatments compared to the 2.8 kg treatments (>18 g pot -1 vs . ∼12 g pot -1 ) and also greater in the topsoil treatment compared to the subsoil treatment (24.0 g pot -1 vs . 18.6 g pot -1 ), resulting in significantly higher phytomining. Soil depth had no statistically significant effect on shoot and root yield. Subsoil fertilization increased yield (25.8 g pot -1 vs . 19.7 g pot -1 ), enough to suggest that further research is warranted to optimize Ni phytomining. This study confirms the importance of soil volume and root access to the subsoil when evaluating the potential for Ni phytomining by Odontarrhena species. The use of small pots may lead to an underestimation of phytomining potential.