Microbial response to designer biochar and compost treatments for mining impacted soils

The Oronogo-Duenweg mining belt is a designated United States Environmental Protection Agency Superfund site due to lead-contaminated soil and groundwater by former mining and smelting operations.Sites that have undergone remediation-in which the O,A,and B horizons have been removed alongside the lead contamination-have an exposed C horizon and are incalcitrant to revegetation efforts.Soils also continue to contain quantifiable Cd and Zn concentrations.To improve soil conditions and encourage successful site revegetation,our study employed three biochars,sourced from different feedstocks(poultry litter,beef cattle manure,and lodgepole pine),at two rates of application(2.5%,and 5%),coupled with compost(0%,2.5%and 5%application rates).Two plant species-switchgrass(Panicum virgatum)and buffalograss(Bouteloua dactyloides)-were grown in the amended soils.Amendment of soils with poultry litter biochar applied at 5%resulted in the greatest reduction of soil bioavailable Cd and Zn.Above-ground biomass yields were greatest with beef cattle manure biochar applied at 2.5%with 5%compost,or with 5%biochar at 2.5%and 5%compost rates.Maximal microbial biomass was achieved with 5%poultry litter biochar and 5%compost,and microbial communities in soils amended with poultry litter biochar distinctly clustered away from all other soil treatments.Additionally,poultry litter biochar amended soils had the highest enzyme activity rates forβ-glucosidase,N-acetyl-β-D-glucosaminidase,and esterase.These results suggest that soil reclamation using biochar and compost can improve mine-impacted soil biogeophysical characteristics,and potentially improve future remediation efforts.

Feedstock choice,pyrolysis temperature and type influence biochar characteristics:a comprehensive meta-data analysis review

Various studies have established that feedstock choice,pyrolysis temperature,and pyrolysis type influence final biochar physicochemical characteristics.However,overarching analyses of pre-biochar creation choices and correlations to biochar characteristics are severely lacking.Thus,the objective of this work was to help researchers,biochar-stakeholders,and practitioners make more well-informed choices in terms of how these three major parameters influence the final biochar product.Utilizing approximately 5400 peer-reviewed journal articles and over 50,800 individual data points,herein we elucidate the selections that influence final biochar physical and chemical properties,total nutrient content,and perhaps more importantly tools one can use to predict biochar’s nutrient availability.Based on the large dataset collected,it appears that pyrolysis type(fast or slow)plays a minor role in biochar physico-(inorganic)chemical characteristics;few differences were evident between production styles.Pyrolysis temperature,however,affects biochar’s longevity,with pyrolysis temperatures>500℃ generally leading to longer-term(i.e.,>1000 years)half-lives.Greater pyrolysis temperatures also led to biochars containing greater overall C and specific surface area(SSA),which could promote soil physico-chemical improvements.However,based on the collected data,it appears that feedstock selection has the largest influence on biochar properties.Specific surface area is greatest in wood-based biochars,which in combination with pyrolysis temperature could likely promote greater changes in soil physical characteristics over other feedstock-based biochars.Crop-and other grass-based biochars appear to have cation exchange capacities greater than other biochars,which in combination with pyrolysis temperature could potentially lead to longer-term changes in soil nutrient retention.The collected data also suggest that one can reasonably predict the availability of various biochar nutrients(e.g.,N,P,K,Ca,Mg,Fe,and Cu)based on feedstock choice and total nutrient content.Results can be used to create designer biochars to help solve environmental issues and supply a variety of plant-available nutrients for crop growth.