Carbon benefits completely offset by nitrogen fertilization induced greenhouse gas emissions in Chinese main cropping systems

Bing Gao1,2, Lilai, Xu1,2, Wei, Huang1,2, Xiaotang Ju3*, Shenghui Cui1,2*

1 Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, PR China

2 Xiamen Key Lab of Urban Metabolism, Xiamen 361021, PR China

*Corresponding author: Shenghui Cui

Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, P.R. China.

Phone: +86-592-6190957; Fax: +86-592-6190977.

E-mail: [email protected]

3 College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China

*Corresponding author: Xiaotang Ju and Shenghui Cui

College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.

Phone: +86-10-20192006; Fax: +86-10-20191016.

E-mail: [email protected]

Abstract

Cropland soil is recognized as a potential major contributor to mitigation global warming by using soil as a carbon sink to sequester carbon dioxide in recent years. Large amount of studies have reported that the soil organic carbon (SOC) content in Chinese cropland soil was increased. While the climate benefits of carbon sequestration in agricultural soils was offset by the N2O emissions from greater use of fertilizer and CO2-eq releases during the manufacture and distribution of the large amounts of applied fertilizer. In this study, we calculate the net GWP of the Chinese main cropping systems by reviewing the studies on soil GHG emissions, CO2-eq emissions and SOC change, to see the integrate effect of cropping systems on GHG emissions. The results showed that the Chinese main cropping systems were large source of CO2-eq, fall in a range of 2209 ± 2557 kg CO2-eq ha-1 yr-1 for MNE to 23581 ± 16925 kg CO2-eq ha-1 yr-1 for GV, following the rank of MNE < MNW < WM < SR < RR < RW < OV < DR < GV. N2O emissions, CO2-eq emissions from the manufacture and distribution of N fertilizer, power used for irrigation were the top three sources of CO2-eq, they totally contribute to 86.6–93.6% of the TPCE in five dry croplands cropping systems. But four rice-based cropping systems, CH4 emissions become one of the large contributors of TPCE except the top three sources of CO2-eq in dry land cropping systems.