Spatiotemporal Dynamics of Carbon Footprint of Main Crop Production in China

As a major agricultural country, the comprehensive accounting of the dynamics and composition of the carbon footprint of major crops in China will provide a decision-making basis for environmental management and agricultural green development in the whole process of the major crop production system in China. To investigate the spatiotemporal dynamics of the carbon footprint for major crops in China, a life cycle-based carbon footprint approach was used to evaluate the carbon footprint per unit area (CF) and per unit yield (CF) of eight crops for the period of 1990 to 2019. Our results showed that the CF for all major crops showed an increasing trend with time before 2016 but slowly decreased afterward, while the CF decreased by 16-43% over the past 30 years due to the increase in crop yield. The three main grain crops, rice (4871 ± 418 kg CO₂-eq · ha^-1), wheat (2766 ± 552 kg CO₂-eq · ha^-1), and maize (2439 ± 530 kg CO₂-eq · ha^-1), showed the highest carbon footprint and contribution to the total greenhouse gas (GHG) emissions, mainly due to their larger cultivated areas and higher fertilizer application rates. CH₄ emission was the major component of the carbon footprint for rice production, accounting for 66% and 48% of the CF and CF, respectively, while fertilizer production and usage were the largest components of carbon footprint for dryland crops, making up to 26-49% of the CF and 26-50% of the CF for different crops. The present study also highlighted the spatial and temporal patterns of the carbon footprint for major crops in China, which could serve as references for the development of best management practices for different crop production in China, to mitigate agricultural GHG emission and to pursue low-carbon agriculture.