Integrating organic fertilizers in maize-mung bean intercropping: implications for soil carbon dynamics and greenhouse gas reduction

Organic fertilizers have great potential to improve crop production while reducing greenhouse gas (GHG) emissions in agroecosystems. To study their effect on GHG emissions, a field experiment over a two-year period (2021 and 2022) was carried out to quantify carbon dioxide (CO2) and nitrous oxide (N2O) emissions. Experimental treatments included: (i) two types of organic fertilizers [wheat residue (WR) and sheep manure (SM)]; and (ii) three cropping systems [monocropping of maize (Zea mays L., Ma) and mung bean (Vigna radiata (L.) R. Wilczek, Mu), and their intercropping (Ma + Mu)]. Total crop biomass and its carbon (C) and nitrogen (N) content, soil CO2 and N2O emissions, soil temperature and moisture were measured. The results showed that Ma + Mu_WR significantly reduced cumulative CO2 emissions by 36% and 28% compared to the Ma_WR and Mu_WR, espectively. Similarly, Ma + Mu_SM reduced soil CO2 emissions by 38% and 70%compared to Ma_SM and Mu_SM, respectively. In addition, Ma + Mu_WR had 69% and 71% lower cumulative N2O emissions than Ma_WR and Mu_WR, respectively, while Ma + Mu_SM showed 48% and 55% lower emissions than Ma_SM and Mu_SM, respectively. WR application significantly increased C input and the C input/output. In the Mu, WR fertilizer led to a significant reduction in both C output and total C emitted, whereas in Ma + Mu, these parameters were not affected by the type of organic fertilizers. In Ma, C output was higher under WR than SM, but total C emitted remained unaffected. This study suggests that integrating organic fertilizer into an intercropping system provides a sustainable and environmentally friendly approach to effective GHG mitigation.