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Biochar compost blends facilitate switchgrass growth in mine soils by reducing Cd and Zn bioavailability
Citation:
Novak, J., J. Ippolito, D. Watts, G. Sigua, T. Ducey, AND Mark G Johnson. Biochar compost blends facilitate switchgrass growth in mine soils by reducing Cd and Zn bioavailability. Biochar Journal. Ithaka Institute for Carbon Intelligence , Arbaz, Switzerland, 1(1):97-114, (2019). https://doi.org/10.1007/s42773-019-00004-7
Impact/Purpose:
Biochar and compost amendments have emerged as potential remediation agents for sequestering heavy metals in mine spoils or in mine impacted soils. This study evaluated the ability of three biochar types produced from poultry litter, beef cattle manure, and lodgepole pine feedstocks, mixed into metal contaminated soils from Webb City, MO, with or without compost, on their ability to sequester Cd and Zn to levels that would allow switchgrass growth in a mine-impacted soil. Key findings were that the biochars differed greatly in their ability to reduce H2O and bioavailable Cd and Zn—poultry litter and beef cattle manure biochar were more effective at reducing extractable Cd and Zn concentrations than lodgepole pine biochar. This condition was related to the ability of these two biochars to raise soil pH to > 5 which reduced the solubility of Cd and Zn and hence lowered their extractable concentrations. The greatest switchgrass and above ground biomass and root production occurred in soils treated with 2.5 and 5% biochar from poultry litter and beef cattle manure plus 5% compost. In general, compost by itself was able to reduce soil extractable Cd and Zn concentrations and total Cd and Zn in switchgrass shoots particularly at the 5% application rate. This study corroborates the finding that biochars should be carefully designed to optimize their potential to modify soil conditions (i.e., increase pH, etc.) to greatly reduce bioavailable Cd and Zn concentrations in mine-impacted soils. If adopted, this paradigm can optimize the selection and application of the most effectual biochar in a mine spoil remediation plan.
Description:
Purpose Biochars have the potential to reclaim mine-impacted soils; however, their variable physico-chemical properties incite speculation about their successful remediation performance. This investigation examined the capability of biochars produced from three different feedstocks along with a compost blend to improve switchgrass growth conditions in a mine-impacted soil by examining influences on soil pH, grass metal contents, and soil extractable metal concentrations. Materials and methods Cadmium (Cd) and zinc (Zn) contaminated mine soil was collected from a site near Webb City, Missouri, USA--a location within the Tri-State Mining District. In a full factorial design, soil was treated with a 0, 2.5, and 5% (w/w) compost mixture (wood chips + beef cattle manure), and 0, 2.5% and 5% of each biochar pyrolyzed from beef cattle manure, poultry litter and lodgepole pine feedstocks. Switchgrass (Panicum virgatum, 'Cave-In-Rock' variety) was grown in a greenhouse for 50 days and mass of shoots (above ground biomass) and roots was assessed, while soil pH, deionized H2O- and 0.01M CaCl2-extractable Cd and Zn concentrations were measured. Results and discussion Poultry litter biochar and compost had the greatest ability to raise soil pH (from 4.40 to 6.61), beef cattle manure biochar and compost moderately raised pH (from 4.4 to 5.92), and lodgepole pine biochar and compost weakly raised pH (from 4.40 to 5.05). Soils treated with beef cattle manure biochar, poultry litter biochar significantly reduced deionized H2O- and 0.01 M CaCl2-extractable Cd and Zn concentrations, while lodgepole pine biochar treated soils showed mixed results. Switchgrass shoot and root masses were greatest in soil treated with compost in combination with either beef cattle manure biochar or poultry litter biochar. Soils treated with 5% beef cattle manure biochar + 5% compost had greater reductions in total Cd and Zn concentrations measured in switchgrass shoots and roots compared to the other two treatments. Conclusions The three biochars and compost mixtures applied to heavy metal, mine-impacted soil had considerable performance dissimilarities for improving switchgrass productivity. Switchgrass growth was noticeably improved after treatment with compost in combination with biochar from beef cattle manure or poultry litter. This may be explained by the increased soil pH that promoted Zn and Cd precipitation and organic functional groups that reduced soil available heavy metal concentrations. Our results imply that creating designer biochars is an important management component in developing successful mine site phytostabilization programs.
URLs/Downloads:
DOI: Biochar compost blends facilitate switchgrass growth in mine soils by reducing Cd and Zn bioavailability