Reducing greenhouse gas emissions from a wheat–maize rotation system while still maintaining productivity Jianzheng Li a,b , Enli Wang b, ⁎, Yingchun Wang a , Hongtao Xing b , Daolong Wang a , Ligang Wang a, ⁎, Chunyu Gao a a CAAS-UNH Joint Laboratory for Sustainable Agro-Ecosystem/Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China b CSIRO Sustainable Agriculture Flagship, GPO Box 1666, Canberra, ACT 2601, Australia abstract article info Article history: Received 24 August 2015 Received in revised form 2 March 2016 Accepted 13 March 2016 Available online xxxx High-input agriculture in China has successfully increased crop productivity in the past decades, but at a significant environmental cost. It is essential to improve management strategies to mitigate greenhouse gas (GHG) emissions and other environmental costs, while maintaining grain yields. However, there is a lack of studies to evaluate mitigation strategies under long-term climate variability. This paper combines field experimental data and soil–plant systems modeling to investigate the potential for improving water and nitrogen management of a wheat–maize double cropping system in North China Plain. The APSIM model was calibrated against the data and then applied to simulate crop yield and N 2 O emissions from soil in response to irrigation and nitrogen inputs. Our results show that the N fertilizer rate and irrigation amount under the local farmer practice could be reduced by 28% and 14% without sacrificing crop yield. This in turn led to a reduction in GHG emissions by 31%, mainly attrib- uted to the decrease in emissions from the production and transportation of N fertilizer and direct N 2 O emissions from soil. Additionally, the results indicate that the direct N 2 O emissions from soil was positively correlated with N inputs, implying an increasing emission factor (N 2 O produced per unit of N input) with N application rates. It is concluded that potential exists to optimize N fertilizer rate and irrigation amount to reduce GHG emissions while still maintaining crop yield in the agro-ecosystems in North China Plain. © 2016 Published by Elsevier Ltd. Keywords: Grain yield Greenhouse gas emissions Nitrogen Irrigation APSIM 1. Introduction Increases in agricultural inputs to produce more food and satisfy global demand has caused substantial greenhouse gas (GHG) emissions. It is responsible for 10–12% of total global anthropogenic emissions of GHG, and for approximately 60% of nitrous oxide (N 2 O) and 50% of methane (CH 4 ) emissions (IPCC, 2007, 2014). In China, GHG emissions from agricultural production systems in 2005 account for more than 15% of China's total GHGs, nearly 90% of N 2 O and 60% of CH 4 emissions (Wang et al., 2010a). The North China Plain (NCP) is one of the most intensive agricultural regions in China, providing more than 50% and 33% of nation's wheat and maize production (Liang et al., 2011). It con- tributes a large portion to the national total GHG emissions, especially N 2 O. It is important to improve the agricultural management to increase or maintain productivity, while reducing the associated environmental costs. In the NCP, approximately 70% of the total cultivated land is under a winter wheat–summer maize cropping rotation (Zhang et al., 2006). The total N fertilizer inputs are as high as 600 kg N ha -1 yr -1 (Zhong et al., 2006) and irrigation water use in some regions can reach 420 mm per year (Liu et al., 2004). The high inputs of synthetic N fertilizer and irrigation water have led to increased N 2 O emissions (Zhang et al., 2014), accompanied by the energy costs and CO 2 emissions associated with lifting water from wells for irrigation and the production and trans- port of N fertilizer (Lal, 2004; Zhang et al., 2013). Additionally, depletion of groundwater resources and pollution of surface and groundwater bodies have caused serious environmental and ecological problems (Liu et al., 2001, 2005). In recent years, China's population growth has slowed (Peng, 2011) and China is becoming increasingly self-sufficient in terms of grain production. There is an urgent need to re-assess the management strategies to improve the eco-efficiency of the cropping systems, that is, to maintain the same productivity with less GHG emissions and other envi- ronmental costs. While a few recent studies have attempted to address these issues, there is still a lack of knowledge to assess management practices under long-term climate variability. Chen et al. (2014) showed that reduction in GHG emissions per unit yield production could be achieved by optimizing N applications based on data from 1 to 4 years experiments, with no detailed information on the impact of long-term climate variabil- ity on agricultural inputs and crop productivity. Li et al. (2008) simulated the response of N 2 O emissions to N fertilizer application and climatic variability using the WNMM model, while Li et al. (2010) analyzed the potential for reducing GHG emissions based on long-term simulations of Agricultural Systems 145 (2016) 90–98 ⁎ Corresponding authors. E-mail addresses: Enli.Wang@csiro.au (E. Wang), wangligang@caas.cn (L. Wang). http://dx.doi.org/10.1016/j.agsy.2016.03.007 0308-521X/© 2016 Published by Elsevier Ltd. 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