Emergy−based efficiency and sustainability assessments of diversified multi−cropping systems in South China

Designing diversified multi-cropping systems is critical for making full use of natural resources on the limited cultivated land to achieve more agricultural products in a sustainable way. However, information is still lacking on whether the higher multi-cropping index possibly decreases the use efficiency of resources and the sustainability of the cropping system due to more agricultural inputs on limited farmland. Therefore, this study introduced the emergy evaluation and designed two trials to quantitatively compare the efficiency and sustainability of different multi-cropping systems in South China, where double-rice was used as a control (CK). Trial 1 included peanut−rice (PRF), peanut−rice/ryegrass × milk vetch mixture (1:1) (PRM1), and peanut−rice/ryegrass × milk vetch mixture (1:2) (PRM2). Trial two included maize−rice (MRF), maize−rice/ryegrass × milk vetch mixture (1:1) (MRM1), and maize−rice/ryegrass × milk vetch mixture (1:2) (MRM2). In trial 1, compared to CK, the annual productivity of PRF decreased 15.38%, while both PRM1 and PRM2 increased 10.49%. Results illustrated that the annual productivity of the MRF, MRM1, and MRM2 systems in trial 2 were improved by 53.85%–85.31% compared to the CK. Meanwhile, the efficiency of the maize-based cultivation patterns (MRF, MRM1, and MRM2) to use nonrenewable resources was increased by 23.56%–24.62% compared to the conventional double-rice system. Moreover, the emergy sustainability index (ESI) in MRM1, and MRM2 systems were 175.63% and 175.51% higher than the CK, respectively. The ESI of PRF, PRM1, and PRM2 were 12.13%, 118.20% and 118.05% higher than CK, respectively. In general, the MRM1 and MRM2 showed the highest efficiency and sustainability compared to other cropping patterns. The key points to improve the efficiency and sustainability of multi-cropping systems were to optimize the fertilizer and labor inputs. This study provided valuable information for the development of diversified multi-cropping systems in South China. It was also a reference for the development of sustainable agriculture in the subtropical agricultural system in the world.