Acidic sandy soil improvement with biochar — A microcosm study Mónika Molnár a, ⁎, Emese Vaszita a , Éva Farkas a , Éva Ujaczki a , Ildikó Fekete-Kertész a , Mária Tolner a , Orsolya Klebercz a , Csaba Kirchkeszner a , Katalin Gruiz a , Nikolett Uzinger b , Viktória Feigl a a Budapest University of Technology and Economics, Faculty of Chemical Technology and Biotechnology, Department of Applied Biotechnology and Food Science, H-1111 Budapest, Műegyetem rkp. 3, Hungary b Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, H-1022 Budapest, Herman Ottó street 15, Hungary HIGHLIGHTS • Biochar treatment is an innovative option to improve acidic sandy soils worldwide. • The complex methodology supported selection of the biochar for field application. • 0.5% grain husk–paper fibre sludge biochar with compost was the most effective. • 1% grain husk–paper fibre sludge biochar improved physico-chemical soil properties. • 1% biochar did not pose risk to soil biota. abstract article info Article history: Received 12 September 2015 Received in revised form 13 January 2016 Accepted 15 January 2016 Available online xxxx Biochar produced from a wide range of organic materials by pyrolysis has been reported as a means to improve soil physical properties, fertility and crop productivity. However, there is a lack of studies on the complex effects of biochar both on the degraded sandy soil physico-chemical properties and the soil biota as well as on toxicity, particularly in combined application with fertilizer and compost. A 7-week microcosm experiment was conducted to improve the quality of an acidic sandy soil combining vari- ations in biochar types and amounts, compost and fertilizer application rates. The applied biochars were produced from different feedstocks such as grain husks, paper fibre sludge and wood screenings. The main pur- pose of the microcosm experiment was to assess the efficiency and applicability of different biochars as soil amendment prior to field trials and to choose the most efficient biochar to improve the fertility, biological activity and physical properties of acidic sandy soils. We complemented the methodology with ecotoxicity assessment to evaluate the possible risks to the soil as habitat for microbes, plants and animals. There was clear evidence of biochar-soil interactions positively affecting both the physico-chemical properties of the tested acidic sandy soil and the soil biota. Our results suggest that the grain husk and the paper fibre sludge biochars applied to the tested soil at 1% and 0.5 w/w% rate mixed with compost, respectively can supply a more liveable habitat for plants and soil living an- imals than the acidic sandy soil without treatment. © 2016 Elsevier B.V. All rights reserved. Keywords: Biochar Acidic sandy soil Soil physico-chemical properties Ecotoxicity Soil improvement 1. Introduction Biochar has been extensively investigated due to its many potential- ly advantageous properties which make it suitable for soil amendment, carbon sequestration, contaminant and heavy metal removal, construc- tion and other innovative applications (Lehmann, 2007; Gaunt and Lehmann, 2008). Biochar amendment in soil may improve soil physical and chemical (Hass et al., 2012; Laird et al., 2010; Liang et al., 2006) and biological properties (Mitchell et al., 2015; Watzinger et al., 2014), nutrient- and water holding capacity, pH buffering capacity as well as soil fertility and plant productivity (Glaser et al., 2002; Lehmann et al., 2003; Major et al., 2010; Yao et al., 2012; Xu et al., 2012). Furthermore biochar may decrease exchangeable acidity and exchangeable aluminium (Al 3+ ) in soil (Novak et al., 2009; Zhao et al., 2015) and control the mo- bility of environmental pollutants (Lehmann et al., 2006; Verheijen et al., 2010; Inyang et al., 2010; Van Zwieten et al., 2010). Some studies (Case et al., 2015; Gurwick et al., 2013; Woolf et al., 2010) have confirmed that biochar amendment contributes to the efforts to reduce agricultural greenhouse gas emissions and therefore mitigate anthropo- genic climate change. The interactions between biochar and soil and the effects on soil physical properties such as water retention, hydraulic conductivity Science of the Total Environment xxx (2016) xxx–xxx ⁎ Corresponding author at: H-1111 Budapest, Szent Gellért sqr. 4., Hungary. E-mail address: mmolnar@mail.bme.hu (M. Molnár). STOTEN-19104; No of Pages 11 http://dx.doi.org/10.1016/j.scitotenv.2016.01.091 0048-9697/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Please cite this article as: Molnár, M., et al., Acidic sandy soil improvement with biochar — A microcosm study, Sci Total Environ (2016), http:// dx.doi.org/10.1016/j.scitotenv.2016.01.091