Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/27/2014
Publication Date: 6/27/2014
Citation: Weyers, S.L., Spokas, K.A., Gaskin, J., Collins, H.P., Cantrell, K.B. 2014. Biochar aging reduces earthworm avoidance [abstract]. The 10th International Symposium on Earthworm Ecology. p. 120.
Technical Abstract: Biochar, a black carbon substance produced by the pyrolysis of organic feedstocks, has been used in many soil improvement strategies ranging from nutrient addition to sequestration of C. Simple toxicity studies and laboratory preference/avoidance assays are recommended but results rarely reported. In fact, the majority of available reports using biochar as a soil amendment in the presence of earthworms lack any mention of positive or negative direct effects on the earthworms. The lack of this data is possibly due to a lapse in methodology to include pre and post incubation earthworm weight or abundance counts. Of note, however, many studies focus on wood-based biochars or charcoals. Earthworm preference/avoidance assays were conducted with a wide variety of biochars, using commodity and animal co-product feedstocks, including pine chips, nut shells, grain hulls, shrimp processing waste, dairy manure, and poultry manure. The assays consisted of sandy loam or silty clay loam soils without or with biochar mixtures ranging from 0.5 to 10% char. The majority of assays indicated the earthworms avoided all animal co-product-based feedstocks at concentrations exceeding 2%, but showed no preference for or against pine chip-based biochars. Deconstructed soil and biochar-soil mixtures were maintained separately in the laboratory and the preference-avoidance assays repeated after a period of three or more years. Earthworms no longer showed preference or avoidance of biochar-soil mixtures above the 2% threshold, indicating that the conditions causing aversion had dissipated. Interestingly, assays repeated with some of the original biochars maintained in sealed packaging for the same period of time still induced earthworm aversion. These findings indicate that co-products of pyrolysis can be pre-screened, and detoxified by aging before land application to avoid unknown but potentially negative impacts.