Comparison of three tillage systems in the wheat-maize system on carbon sequestration in the North China Plain Ming-Yuan Zhang a, b , Fu-Jun Wang a, b , Fu Chen a, b , Maphorogetja P. Malemela a, b , Hai-Lin Zhang a, b, * a College of Agronomyand Biotechnology, China Agricultural University, Beijing 100193, China b Key Laboratory of Farming Systems, Ministry of Agriculture, Beijing 100193, China article info Article history: Received 25 March 2012 Received in revised form 8 April 2013 Accepted 22 April 2013 Available online 6 May 2013 Keywords: Soil carbon storage Soil carbon sequestration rate Carbon footprint Hidden carbon cost No tillage abstract Whether farmland serves as a carbon (C) source or sink depends on the balance of soil organic carbon (SOC) sequestration and greenhouse gas (GHG) emissions. Tillage practices critically affect the SOC concentration, SOC sequestration rate and soil carbon storage (SCS). The objective of this paper is to assess the tillage effects on SOC sequestration, SCS and C footprint. Tillage experiments were established on a double cropping system of winter wheat (Triticum aestivum L.) and summer corn (Zea mays L.) in the North China Plain since 2001 with three treatments: no tillage (NT), rotary tillage (RT) and conventional tillage (CT). In order to assess SOC sequestration efficiency under different tillage systems, SCS, SOC sequestration rate, hidden carbon cost (HCC), indexes of sustainability (I s ) and C productivity (CP) were computed in this study. Results showed that the SCS increased with years of residue retention. The SCS attained the highest degree in 2007, which was about 25%e30% higher than that in 2004. The net SOC sequestration rate was the highest in NT and lowest in CT, while HCC was lowest under NT and highest under CT. The value of I s for CT, RTand NT treatments was 1.46,1.79 and 1.88, respectively, and that of CP was 11.02,12.79 and 10.57, respectively. Therefore, it can be concluded that NT provides a good option for increasing SOC sequestration for agriculture in the North China Plain. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Global warming has become a concerning issue due to the po- tential impacts on resources, agriculture, energy use, weather patterns and environment etc. Massive greenhouse gas (GHG) emissions have been released from rapidly developing industry and agriculture (IPCC, 2007). Agriculture is the largest terrestrial biome, occupying as much as 35% of the earth’s land area (Asner et al., 2004). Agricultural cleaner production and farm product con- sumption in relation to environmental impacts have become the focus of attention of scientists and policy makers (Lal, 2003). The processes of crop production influence GHG emissions and soil organic carbon (SOC) sequestration. Cleaner production man- agement in agro-ecosystems can play a major role in reducing the rate of enrichment of atmospheric GHG because of the huge po- tential of soil carbon storage (SCS) in soils (Lal, 2003, 2007). The soil carbon (C) pool can be a source or sink for an atmospheric C pool, depending on land use and management (Schimel et al., 2001). Hence, proper management practices are encouraged to seques- trate atmospheric C into the soil (Lal, 2004a). Numerous cleaner production technologies (e.g., conservation tillage, reasonable fertilization and crop rotation) can reduce GHG emissions, increase SOC sequestration, enhance SCS and improve crop yield (Schlesinger, 1999). Conservation tillage, one of recom- mended management practices (RMPs), has become a major technology for sustainable agriculture because of its numerous benefits (e.g., reducing soil erosion, saving water/labor/time/fuel and improving soil quality) (Fowler and Rockstrom, 2001; Hargrove, 1990; Lal et al., 1990). Tillage can strongly alter soil properties and SOC distribution along with attendant changes in characteristics of GHG emissions and SCS (Ussiri and Lal, 2009). Most previous studies have shown that no tillage (NT) and mini- mum tillage can increase SOC because of minimal soil disturbance and residue retention (Duiker and Lal, 1999; Lal and Kimble, 1997; Puget and Lal, 2005). The concept of C footprint has been used in many studies related to climate change. Carbon footprint is the total set of GHG * Corresponding author. College of Agronomy and Biotechnology, China Agri- cultural University, Beijing 100193, China. Tel./fax: þ86 10 62733316. E-mail address: hailin@cau.edu.cn (H.-L. Zhang). Contents lists available at SciVerse ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro 0959-6526/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jclepro.2013.04.033 Journal of Cleaner Production 54 (2013) 101e107