1 Deinition, analysis, and certiication of biochar quality are crucial to the agronomic acceptance of biochar. While most biochars have a positive impact on plant growth, some may have adverse efects due to the presence of phytotoxic compounds. Conversely, some biochars may have the ability to adsorb and neutralize natural phytotoxic compounds found in soil. We evaluated the efects of biochars on seedling growth and absorption of allelochemicals present in corn (Zea mays L.) residues. Corn seeds were germinated in aqueous extracts of six biochars produced from varied feedstocks, thermochemical processes, and temperatures. Percent germination and shoot and radicle lengths were evaluated at the end of the germination period. Extracts from the six biochars had no efect on percent germination; however, extracts from three biochars produced at high conversion temperatures signiicantly inhibited shoot growth by an average of 16% relative to deionized (DI) water. Polycyclic aromatic hydrocarbons detected in the aqueous extracts are believed to be at least partly responsible for the reduction in seedling growth. Repeated leaching of biochars before extract preparation eliminated the negative efects on seedling growth. Biochars difer signiicantly in their capacity to adsorb allelochemicals present in corn residues. Germination of corn seeds in extracts of corn residue showed 94% suppression of radicle growth compared to those exposed to DI water; however, incubation of corn residue extracts with leached biochar for 24 h before initiating the germination test increased radicle length 6 to 12 times compared to the corn residue extract treatments. Germination tests appear to be a reliable procedure to diferentiate between efects of diferent types of biochar on corn seedling growth. Germination Tests for Assessing Biochar Quality N. Rogovska,* D. Laird, R. M. Cruse, S. Trabue, and E. Heaton B iochar, one of the coproducts of pyrolysis, consists of up to 90% carbon and is a potential soil amend- ment for increasing productivity while simultaneously sequestering large amounts of carbon (Lehmann, 2007; Laird, 2008; Rogovska et al., 2011). Application of biochar to soils has been shown to reduce compaction, increase water and nutrient holding capacity, enhance biological activity, increase crop yields, and reduce nitrous oxide emissions (Chan et al., 2007; Lehmann and Joseph, 2009; Spokas and Reicosky, 2009; Laird et al., 2010a,b; Rogovska et al., 2011). Biochar has also been shown to increase sorption of agrochemicals and thus reduce their leaching potential (Cao et al., 2009; Laird et al., 2010b). Various residual forms of organic material including manure, urban yard waste, and crop residues, as well as dedi- cated energy crops such as miscanthus (Miscanthus giganteus J.M. Greef & Deuter ex Hodkinson & Renvoize) and switch- grass (Panicum virgatum L.), can be utilized as a feedstock for the pyrolysis process (Roberts et. al., 2010). Characteristics and composition of the feedstock have an impact on the physical and chemical properties of the biochar coproduct; moreover, pyrolysis conditions—temperature, heating rate, residency time, oxygen ratio, and type of reactor—inluence biochar characteristics and quality as well (Goyal et al., 2008; Gaskin et al., 2008, 2010). Biochars thus vary in physical composition, carbon, ash, and volatile matter contents, pH, elemental composition, and chem- ical structure (Joseph et al., 2010; Spokas, 2010). Diferences in these variables can have profound inluence on the behavior of biochars in soils, their stability, and efect on soil microbiological, chemical, and physical properties (Spokas and Reicosky, 2009; Spokas et al., 2010). To date, proximate analysis, which parti- tions biochar into ixed carbon, volatile matter, ash, and water, has been the dominant analytical method used for assessing bio- char quality. Despite great variability in biochar characteristics, generally accepted methods of evaluating biochar quality for use as a soil amendment are lacking. here are many uncertainties in deining “biochar quality.” For example, biochar used for carbon sequestration purposes would be evaluated based on its decomposition rates and its efect on the native soil organic matter pool, whereas biochar used as a soil conditioner would be evaluated on its efect on soil physical properties such as bulk density, water holding capacity, Abbreviations: DI, deionized water; GC-MS, gas chromatography–mass spectroscopy; PAH, polycyclic aromatic hydrocarbon; TDS, thermal desorption. N. Rogovska, D. Laird, R.M. Cruse, and E. Heaton, Dep. of Agronomy, Iowa State Univ., Ames, IA 50011; S. Trabue, USDA–ARS, Natl. Lab. for Agriculture & Environment, Ames, IA 50011. Assigned to Associate Editor Warren Busscher. Copyright © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. J. Environ. Qual. 41:1–9 (2012) doi:10.2134/jeq2011.0103 Posted online 22 Mar. 2011. Received 16 June 2010. *Corresponding author (natashar@iastate.edu). © ASA, CSSA, SSSA 5585 Guilford Rd., Madison, WI 53711 USA Journal of Environmental Quality SPECIAL SUBMISSIONS