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Title: Earthworms, Microbes and the Release of C and N in Biochar Amended Soil

Author
item Weyers, Sharon
item GASKIN, JULIA - University Of Georgia
item LIESCH, AMANDA - Kansas State University
item DAS, KESHAV - University Of Georgia

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/30/2010
Publication Date: 6/30/2010
Citation: Weyers, S.L., Gaskin, J., Liesch, A.M., Das, K.C. 2010. Earthworms, Microbes and the Release of C and N in Biochar Amended Soil [abstract]. In: Proceedings of the 2010 U.S. Biochar Initiative Conference, June 27-30, 2010, Ames, Iowa. Available: http://www.biorenew.iastate.edu/fileadmin/www.biorenew.iastate.edu/biochar2010/Presentations/Weyers_USBI_2010.pdf

Interpretive Summary:

Technical Abstract: Land application of biochar has the potential to increase soil fertility and sequester carbon. It is unclear how soil microbes and earthworms interact with biochar and affect release or retention of nutrients. In order to determine the effects and interactions among soil microbes, earthworms, and biochar, we designed a three-part evaluation. The first part was to determine if two types of biochar had any toxic impact on growth and survivorship of earthworms (Eisenia fetida) in artificial soil. The second part was to investigate what impacts on the same earthworm species, as well as microbial respiration and biomass, occurred in field-collected soil. The third part will evaluate biochar application to field-collected soil with field-collected earthworms at natural densities. We evaluated pine chip and poultry litter biochars in acidic Tifton and Cecil soils from Georgia. In the first part we determined that biochar derived from poultry litter induced high soil pH and was detrimental to earthworm survivorship and growth; however, pine chip biochar had no effect on the earthworm test species compared to the control soil. In the second part we found that soil respiration decreased with increasing application rate of biochar, and that more respiration occurred when earthworms were present. Although microbial biomass also tended to decline with increasing application rates, it also was slightly elevated where earthworms were present. Nitrogen mineralization increased with increasing biochar application rates with or without worms. This increase, paired with a decline in microbial biomass and earthworm activity, indicated that the microbial biomass may have been mineralized instead of the biochar. In the earthworm-containing treatments, mineralized N may have been released as earthworm nitrogenous waste or mineralized earthworm tissue where earthworm death occurred. Our results indicate the need to consider function of the soil biota in the release of N or sequestration of C in biochar-amended soils.