Comparisons between diversified multicropping systems in terms of crop productivity, economic benefits and carbon footprint in the Pearl River Delta region of South China

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Increasing crop output while emitting fewer greenhouse gases (GHG) from limited farmland has been a major focus of research in world agricultural production. However, information on diversified multicropping systems involving forage in winter fallow fields has rarely been reported in South China. Therefore, in this study we designed three diversified multicropping systems, including maize−rice−fallow (MRF), maize−rice/ryegrass ​× ​milk vetch mixture (1:1) (MRM1) and maize−rice/ryegrass ​× ​milk vetch mixture (1:2) (MRM2), based on a field trial in the Pearl River Delta region of South China during 2021–2023. The annual crop productivity, economic benefits and carbon footprint (CF) of the diversified multicropping system were jointly analyzed. The results showed that the crop productivity of MRM1 and MRM2 was increased by 14.97% and 14.01%, respectively, compared with MRF, and the increase in MRM1 was significant (P ​< ​0.05). Compared with MRF, the economic benefits of MRM1 and MRM2 were increased by 10.15% and 10.29%, respectively, and the differences were not significant. It was found that the higher the planting index is, the lower the CF value. The CF values of MRM1 and MRM2 based on unit area, unit crop productivity and unit economic benefit decreased by 5.13%–22.83%, respectively; this was mainly due to the significant increase in soil organic carbon content by MRM1 and MRM2, which were 4.12% and 15.66% higher than MRF, respectively (P ​< ​0.05). In summary, the introduction of winter forage in the maize‒rice multicropping systems in the Pearl River Delta region of South China could improve crop productivity, increase economic benefits, and reduce the CF. MRM2, the recommended pattern based on the current results, has higher economic efficiency and lower carbon footprint per unit compared to MRM1. This study provides valuable information for the creation of diversified multicropping systems in South China and a reference for the development of sustainable farming systems in tropical subtropical regions worldwide.