The advantages in crop yields and carbon footprints of maize-soybean relay strip intercropping

Intercropping can improve nutrient utilization, but the mechanisms of greenhouse gas (GHG) emissions, energy use, and carbon footprint in rain-fed cereal-legume intercropping remain unclear. Hence, a two-year field trial was conducted to evaluate cropping systems' productivity, carbon footprint, energy inputs, and outputs. The cropping systems include monocropping maize (M) and soybean (S), maize-soybean relay strip intercropping (IMS), and maize-soybean alternate row relay intercropping (CMS). Results showed that the grain yield of the IMS system (9.1 t ha^-1) was three times that of S and resulted from a complementary effect rather than a selection effect. Although the differences in yield between IMS, CMS, and M were insignificant, the land equivalent ratio (LER) of IMS and CMS was higher than one, mainly due to the partial LER of maize. Besides, the economic benefit of IMS was 41.2 % higher than CMS, 48.1 % higher than M, and 119.2 % higher than S, respectively. In IMS, the complementary effect mainly results from the advantages of decreasing direct CO₂ equivalent emissions and indicating CO₂ equivalent emissions, consequently obtaining a lower yield and economic benefit scaled greenhouse gas emissions intensity (GHGI). Furthermore, the net energy output, yield-scaled carbon footprints, yield economic benefit-scaled carbon footprints, and energy output-scaled carbon footprints were 31.4 %, 3.3 %, 25.5 %, and 30.3 % notably lower in IMS than in M, respectively. The complementary effect boosted the advantages in energy productivity, specific energy, energy profitability, and carbon footprint of IMS, but the net energy outputs and energy use efficiency were insignificant between IMS and CMS. The results indicate that the maize-soybean relay strip intercropping provides ways to achieve cleaner production in rain-fed areas.