Carbon emission of maize-based cropping systems in the North China Plain

Abstract

High carbon emission is one of the dominant challenges for sustainable agricultural development in the North China Plain. Maize-based (Zea mays) sustainable cropping systems have recently been developed as water-saving and low carbon cropping systems compared to traditional maize-wheat (Triticum aestivum) cropping. To examine carbon emission of different cropping systems, five maize-based cropping systems were investigated from 2015 to 2017 in this study, which included intercropping of maize and soybean (Glycine max) (MS), relay intercropping of maize with pea (Pisum sativum) (MP) and potato (Solanum tuberosum) (MO), and rotation of maize with ryegrass (Secale cereale) (MR) and spinach (Spinacia oleracea) (MI), with monocropped maize (MM) as the control. Carbon emission of each cropping system per unit area, per kg biomass, and per unit economic output was calculated based on the experimental results, which considered direct emissions of soil greenhouse gas and indirect emissions of agricultural inputs. Results revealed the carbon emission unit area of monocropped maize was 19380.67 kg CO2-eq/ha, and maize-based cropping systems increased by 11%–34% compared to MM, except MS which decreased by 38%. While, the carbon emission per kg biomass and per economic output of the five maize-based cropping systems were decreased by 7%–24% and 18%–61% compared to those of MM (1.04 kg CO2-eq/kg and 8.04 kg CO2/$). The cropping systems showed the order of MS < MI < MR < MO < MP < MM and MI < MO < MR < MP < MS < MM sorted by their annual carbon emission calculated per kg biomass and per economic output, respectively. The direct greenhouse gas emissions from soil were responsible for 76–85% of total carbon emission, which were mostly emitted in the growing period. Results showed that maize-based cropping systems could contribute to cleaner production in terms of biomass and economic output in the North China Plain. These indicate that suitable cropping system can achieve low carbon emission without compromising economic benefits compared to monocropped maize. Intercropping of maize and soybean, relay cropping of maize with potato are recommended in the North China Plain in this study among the treatments.