Abstract
Requirements for mitigation of the continued increase in greenhouse gas (GHG) emissions are much needed for the North China Plain (NCP). We conducted a meta‐analysis of 76 published studies of 24 sites in the NCP to examine the effects of natural conditions and farming practices on GHG emissions in that region. We found that N2O was the main component of the area‐scaled total GHG balance, and the CH 4 contribution was <5%. Precipitation, temperature, soil pH, and texture had no significant impacts on annual GHG emissions, because of limited variation of these factors in the NCP. The N2O emissions increased exponentially with mineral fertilizer N application rate, with y = 0.2389e0.0058x for wheat season and y = 0.365e0.0071x for maize season. Emission factors were estimated at 0.37% for wheat and 0.90% for maize at conventional fertilizer N application rates. The agronomic optimal N rates (241 and 185 kg N ha−1 for wheat and maize, respectively) exhibited great potential for reducing N2O emissions, by 0.39 (29%) and 1.71 (56%) kg N2O‐N ha−1 season−1 for the wheat and maize seasons, respectively. Mixed application of organic manure with reduced mineral fertilizer N could reduce annual N2O emissions by 16% relative to mineral N application alone while maintaining a high crop yield. Compared with conventional tillage, no‐tillage significantly reduced N2O emissions by ~30% in the wheat season, whereas it increased those emissions by ~10% in the maize season. This may have resulted from the lower soil temperature in winter and increased soil moisture in summer under no‐tillage practice. Straw incorporation significantly increased annual N2O emissions, by 26% relative to straw removal. Our analysis indicates that these farming practices could be further tested to mitigate GHG emission and maintain high crop yields in the NCP.
Highlights
Global atmospheric concentrations of greenhouse gases (GHGs) such as CO2, N2O, and CH4 have continued to increase, which has further heightened public and scientific concerns (IPCC, 2014; Wei, Zhang, Chen, Zhang, & Zhang, 2012)
High land productivity in the North China Plain (NCP) has relied on intensive farming practices since the 1980s (Liao, Wu, Meng, Smith, & Lal, 2015), which are characterized by frequent irrigation (Wang, Yu, Wu, & Xia, 2008) and high levels of mineral nitrogen (N) fertilizer application (550– 600 kg N ha−1 year−1; Ju et al, 2009)
In the near future, greater crop yields with reduced GHG emissions must be achieved in China to meet the dual goals of ensuring food security and reducing negative environmental impacts (Chen et al, 2014; The State Council of China, 2016)
Summary
Global atmospheric concentrations of greenhouse gases (GHGs) such as CO2, N2O, and CH4 have continued to increase, which has further heightened public and scientific concerns (IPCC, 2014; Wei, Zhang, Chen, Zhang, & Zhang, 2012). Many site-specific studies have been conducted to explore the impacts of fertilization (Tan et al, 2017; Yan, Yao, Zheng, & Liu, 2015), tillage (Tian et al, 2012; Wei et al, 2012), and crop residues (Hu et al, 2013; Huang, Gao, Christie, & Ju, 2013) on GHG emission and crop yield in the NCP These individual studies were not able to provide a generalized understanding across this large region. Previous meta-analyses for China’s agricultural soils have examined the relationship between natural and farming factors and GHG emissions (Lu, Huang, Zou, & Zheng, 2006; Zhao et al, 2016) They did not focus on winter wheat–summer maize (WW- SM) rotation, the typical and major farming system in the NCP, and their conclusions did not provide technical support for GHG mitigation in the region. We aimed at quantifying the comprehensive responses of GHG emissions to major farming practices and natural factors in the NCP, which will facilitate large crop yields and GHG mitigation in the region
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