TECHNICAL REPORTS 164 Biochar applications to soils can improve soil fertility by increasing the soil’s cation exchange capacity (CEC) and nutrient retention. Because biochar amendment may occur with the applications of organic fertilizers, we tested to which extent composting with farmyard manure increases CEC and nutrient content of charcoal and gasiication coke. Both types of biochar absorbed leachate generated during the composting process. As a result, the moisture content of gasiication coke increased from 0.02 to 0.94 g g −1 , and that of charcoal increased from 0.03 to 0.52 g g −1 . With the leachate, the chars absorbed organic matter and nutrients, increasing contents of water-extractable organic carbon (gasiication coke: from 0.09 to 7.00 g kg −1 ; charcoal: from 0.03 to 3.52 g kg −1 ), total soluble nitrogen (gasiication coke: from not detected to 705.5 mg kg −1 ; charcoal: from 3.2 to 377.2 mg kg −1 ), plant-available phosphorus (gasiication coke: from 351 to 635 mg kg −1 ; charcoal: from 44 to 190 mg kg −1 ), and plant-available potassium (gasiication coke: from 6.0 to 15.3 g kg −1 ; charcoal: from 0.6 to 8.5 g kg −1 ). he potential CEC increased from 22.4 to 88.6 mmol c kg −1 for the gasiication coke and from 20.8 to 39.0 mmol c kg −1 for the charcoal. here were little if any changes in the contents and patterns of benzene polycarboxylic acids of the biochars, suggesting that degradation of black carbon during the composting process was negligible. he surface area of the biochars declined during the composting process due to the clogging of micropores by sorbed compost-derived materials. Interactions with composting substrate thus enhance the nutrient loads but alter the surface properties of biochars. Biochar Afected by Composting with Farmyard Manure Katharina Prost,* Nils Borchard, Jan Siemens, Timo Kautz, Jean-Marie Séquaris, Andreas Möller, and Wulf Amelung B iochar amendments are able to improve biological (Warnock et al., 2007; Kolb et al., 2009; Lehmann et al., 2011), physical (Busscher et al., 2010; Laird et al., 2010), and chemical soil properties, especially in highly weathered, acidic soils (Lehmann et al., 2003a; van Zwieten et al., 2010; Lehmann and Rondon, 2006). In this context, the term biochar refers to any type of charred organic material that is applied to improve soil fertility and/or to sequester carbon (Lehmann et al., 2006; Lehmann and Joseph, 2009; Sohi et al., 2009). Expectations regarding the positive efects of biochar on soil fertility were born from research on so-called Terra Preta soils. hese soils are of anthropogenic origin, embedded as small patches in a landscape that is dominated by highly weathered Oxisols. he Terra Preta soils developed through the impact of the pre-Colum- bian population and are more fertile than the surrounding Oxi- sols due to thicker and darker A-horizons, with elevated stocks of total organic C, N, plant-available P and Ca, higher pH values, and higher cation exchange capacity (CEC) (Sombroek, 1966; Zech et al., 1979; Smith, 1980; Glaser et al., 2001; Lehmann et al., 2003b; Liang et al., 2006). he highly aromatic nature of the Terra Preta–derived organic matter (Zech et al., 1979) has been assigned to the addition of biochar (Glaser et al., 2001). However, the pre-Columbian population did not solely add biochar to the soil. he char was part of a mixture with cooking remains, plant biomass, and excrements (Glaser, 2007; Birk et al., 2011). Little is known about how other organic soil amendments like manure interact with biochar and alter biochar properties. Because freshly produced biochars from wood usually do not show a particularly high potential CEC (Singh et al., 2010), the oxidation of biochar ater its incorporation into soil has been considered as a prerequisite for its adsorption of nutrients (Cheng et al., 2006; Liang et al., 2006). However, this surface oxidation is a slow process that probably lasts several decades (Cheng et al., 2008). Composting might facilitate surface oxi- Abbreviations: AAS, atomic absorption spectroscopy; ANC, acid-neutralizing capacity; BC, black carbon; BPCA, using benzene polycarboxylic acid; CEC, cation exchange capacity; DOM, dissolved organic matter; HTT, highest treatment temperature; TSN, total soluble nitrogen; WEOC, water-extractable organic carbon. K. Prost, N. Borchard, J. Siemens, and W. Amelung, Univ. of Bonn, Institute of Crop Science and Resource Conservation, Soil Science and Soil Ecology, Nussallee 13, 53115 Bonn, Germany; T. Kautz, Univ. of Bonn, Institute of Organic Agriculture, Katzenburgweg 3, 53115 Bonn, Germany; N. Borchard and J.-M. Séquaris, Forschungszentrum Jülich GmbH, Agrosphere Institute, IBG-3, 52425 Jülich, Germany; A. Möller, Federal Institute for Geo-Science and Natural Resources, Stilleweg 2, 30655 Hannover, Germany. Assigned to Associate Editor Joseph Pignatello. Copyright © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA. 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. 42:164–172 (2013) doi:10.2134/jeq2012.0064 Supplemental data ile is available online for this article. Received 13 Feb. 2012. *Corresponding author (kprost@uni-bonn.de). Journal of Environmental Quality ORGANIC COMPOUNDS IN THE ENVIRONMENT TECHNICAL REPORTS