MULTI-SCALE EVALUATION OF LAND USE MANAGEMENT SYSTEMS IN THE UPPER MIDWEST
Location: Soil Management Research
Title: Impact of Two Different Biochars on Earthworm Growth and Survival
Submitted to: Annals of Environmental Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 2010
Publication Date: August 10, 2010
Citation: Liesch, A.M., Weyers, S.L., Gaskin, J.C., Das, K.C. 2010. Impact of Two Different Biochars on Earthworm Growth and Survival. Annals of Environmental Science. 4:1-9.
Interpretive Summary: Biochar is a material created from the thermo-conversion of biomass through pyrolysis (a heating process in the absence of oxygen) for the production of bio-energy. The use of biochar as a soil amendment has been proposed as a means to sequester carbon, thus offsetting the release of CO2 from energy production which may be contributing to climate change. Biochars used as soil amendments for carbon sequestration are often applied at high rates to maximize carbon storage. Management strategies for the use of biochar as a soil amendment are still in development, and the effect of adding biochar to soil on soil organisms, in particular earthworms, is virtually unknown. Standard earthworm toxicity experiments with artificial soil were used to determine if poultry litter and pine chip biochars are detrimental to earthworm survival and growth. Pine chip biochars had no significant effect on earthworm survival and growth, but poultry litter biochars caused earthworm death and weight loss compared to control treatments at application rates above 30 t ac-1 or 13 t carbon per acre (66 metric tons per hectare). The negative impact of biochar on earthworms is likely due to changes in soil pH. Poultry litter biochar also contains salts and potentially toxic substances including zinc and copper that could have impacted earthworm survival. Scientists, land managers, policy makers and others involved in the process will benefit from this research when they develop recommendations for biochar land applications by considering the potential impact on soil biota and taking into account chemical properties particularly pH, metals and ammonia.
The interest in using biochar as a soil amendment to increase soil fertility and sequester C is growing rapidly. Recent research indicates that feedstock and pyrolysis conditions greatly affect the chemical and physical characteristics of biochar. Little work has been conducted on the effects of different biochars on the survival and reproduction of earthworms. The toxicity of a high nutrient (poultry litter) and a low nutrient (pine chip) biochar on Eisenia fetida was evaluated using the EPA artificial soil test at five different application rates of 0%, 50%, 100%, 150%, and 200% of 44.8 t ha-1. This study indicated that at application rates of 150 and 200% poultry litter biochar caused complete mortality. Pine chip biochar, however, had similar survival and weight changes as controls, indicating no significant effect on earthworms. Neither of the biochars tested was actively incorporated by earthworms.