ABSTRACT
Practical phytoextraction and especially phytomining depend on the existence of plants, now called hyperaccumulators, which accumulate exceptionally high concentrations of metals in their shoots, typically 100-fold levels in crop plant species. Phytomining is a related concept in which hyperaccumulator plants are used to both remove soil metals and produce crop biomass containing enough metal to be economically profitable as a metal crop. Ni in ash of hypernickelophore plant shoots is in the matrix of plant nutrients, not the matrix of iron and manganese oxides and silicates of ultramafic soils. The agronomic variables that needed to be characterized experimentally was the planting density which gives the highest shoot Ni yield. Soil cobalt could also be phytoextracted using Alyssum murale, but soil or solution Ni inhibits cobalt phytoextraction, and annual cobalt removal was greatest at low pH in contrast to the higher Ni removal at higher soil pH.
