Accumulation Capacity of Nickel and Zinc in Yerba Mate Cultivated in Soils with Contrasting Parent Materials

Yerba mate (Ilex paraguariensis St. Hill.) has shown a relatively high capacity for micronutrient absorption and could be a candidate for biofortification and combating a lack of micronutrients. To further evaluate the accumulation capacity of Ni and Zn, yerba mate clonal seedlings were grown in containers under five rates of Ni or Zn (0, 0.5, 2, 10, and 40 mg kg-1) with three soils originating from different parent material (basalt, rhyodacite, and sandstone). After 10 months, plants were harvested, divided into component parts (leaves, branches, and roots), and evaluated for 12 elements. The use of Zn and Ni enhanced seedling growth under rhyodacite- and sandstone-derived soils at the first application rate. Application of Zn and Ni resulted in linear increases based on Mehlich I extractions; recovery of Ni was smaller than Zn. Root Ni concentration increased from approximately 20 to 1000 mg kg-1 in rhyodacite-derived soil and from 20 to 400 mg kg-1 in basalt- and sandstone-derived soils; respective increases in leaf tissue were ~ 3 to 15 mg kg-1 and 3 to 10 mg kg-1. For Zn, the maximum obtained values were close to 2000, 1000, and 800 mg kg-1 for roots, leaves, and branches for rhyodacite-derived soils, respectively. Corresponding values for basalt- and sandstone-derived soils were 500, 400, and 300 mg kg-1, respectively. Although yerba mate is not a hyperaccumulator, this species has a relatively high capacity to accumulate Ni and Zn in young tissue with the highest accumulation occurring in roots. Yerba mate showed high potential to be used in biofortification programs for Zn.