Author
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PAUL, ADRIAN - Universite Catholique De Lille |
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Chaney, Rufus |
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BAKLANOV, LLYA - University Of Maryland |
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Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/15/2017 Publication Date: N/A Citation: N/A Interpretive Summary: Phytomining is a technology which uses plants which hyperaccumulate exceptional concentrations of metals to remove metals from contaminated or mineralized soils. Plant ash is an excellent ore for nickel, richer than all traditional nickel ores. ARS developed nickel phytomining technology which uses Alyssum species (can accumulate over 1% nickel in shoots on dry matter basis). The crop is grown like a “hay” crop, cut in June when the plants are at maximum biomass, dried in the field and baled for handling. Improving understanding of hyperaccumulation processes, and optimization of agronomic factors affecting yield of nickel in the biomass (concentration-x-yield) is the goal of continuing research. In the present study, four factors were tested: 1) the effect of double vs. single volume of soil; 2) topsoil vs. subsoil; 3) two layers (topsoil over subsoil) and 4) fertilization of the subsoil. Serpentine topsoil and subsoil were collected for this study from the Soldiers Delight Serpentine Barren near Reistertown, MD. Plants were grown for 3 months before harvest. Bulk soil from before treatments were applied, and soils from individual pots after harvest were analyzed for fertility and for forms of nickel in the soil. Plants grew well on all treatments; shoot yields were higher on double volume treatments and on treatments with subsoil compared to the single volume pots. Nickel concentration (mg per kg dry shoot mass) was not significantly different among the treatments, but yields were significantly different such that the yield of shoot nickel (mg per pot) were substantially higher in double volume and two layer treatments. Even fertilization of subsoil improved yield of nickel in shoots. Many earlier pot experiment on Ni phytomining used smaller pots than needed for observation of the maximum nickel yield in hyperaccumulator Alyssum plants. This study showed that access to a larger volume of topsoil or to serpentine subsoil increases Ni phytomining. Experiments to develop improved production practices should take into account the role of subsoil in practical Ni phytomining. Roots can access nickel in the subsoil so the subsoil of potential phytomining fields should be examined as well as the topsoil. Technical Abstract: Aims: Test the effect of soil volume and presence of subsoil on Ni hyperaccumulation. Methods: A. corsicum Duby was grown for 3 months on Chrome loam topsoil and subsoil from near Reistertown, MD, in a test of growth and Ni accumulation with varied soil masses (2.8 and 5.6 kg pot-1) to study the impact on growth and Ni accumulation. The subsoil position effect was simulated using one 2.8 kg pot on the top of the other. Results: Shoot Ni concentrations were similar for all treatments at 7 g Ni kg-1 DW. Shoot and root yields were significantly higher in 5.6 kg treatments compared to 2.8 kg treatment (>18 g pot-1 vs ~12 g pot-1) and greater in topsoil treatment compared to subsoil (24.0 g pot-1 vs 18.6 g pot-1). Higher yields of shoots gave significantly higher phytoextraction. Depth of soil did not statistically impact shoot and root yield. Fertilization of subsoil caused an increase in yield (25.8 g pot-1 vs 19.7 g pot-1), enough to suggest further research to manage Ni phytomining is needed. Conclusions: This study confirms the importance of soil volume and access to subsoil to assess potential Ni phytomining by Alyssum species. Using small pots underestimates phytomining potential. |
