Sustainable intensification can defuse conflict arising from the limited availability of farmland resources and the inflexible growth of material demand, thereby establishing itself as an effective strategy for nations to ensure food security and promote sustainable development. Considering that research on sustainable intensification focuses primarily on regions with flat and highly consolidated land parcels, there is relatively little exploration in areas with high land fragmentation. However, in regions with significant land fragmentation, the cultivated area per capita is smaller and the human–land contradiction is more pronounced. This makes it all the more worthwhile to investigate the sustainable intensification of these areas. This study focused on a Chinese provincial area and aimed to investigate the operational laws and influencing mechanisms for the sustainable intensification of farmland use. Emergy analyses were conducted to measure the spatial and temporal development patterns of sustainable farmland use intensification in Jiangxi Province during 2007–2021, and to provide a reference for farmland use optimization in other regions of China and worldwide. (1) Compared with in 2007, in 2021, the emergy input of the ecological–economic cultivated area systems in Jiangxi Province decreased by 19.76%, and the emergy output increased by 18.39%. (2) In the past fifteen years, the emergy productivity (EPR) of the ecological and economic system of cultivated land in Jiangxi Province has shown a fluctuating upward trend; compared with in 2007, the EPR in Jiangxi Province in 2021 rose by 58.09%, spatial characteristics from the center to the north and south were reduced, and the gap widened. The emergy yield rate (EYR) of the ecological and economic system of cultivated land in Jiangxi Province has shown an overall upward trend; compared with in 2007, the EYR in Jiangxi Province in 2021 rose by 43.39%, spatial characteristics from the north to the south were reduced, and the gap widened. The Jiangxi Province cultivated land ecological and economic system environmental loading rate (ELR) showed an overall downward trend; compared with in 2007, the ELR in Jiangxi Province in 2021 fell by 30%, spatial characteristics from the north to the south were reduced, and the difference narrowed. The economic efficiency (EE) of Jiangxi Province’s cultivated land ecological and economic system showed a fluctuating downward trend; compared with in 2007, EE in Jiangxi Province in 2021 fell by 29.97%, the spatial characteristics decreased from north to south, and the difference narrowed. Conclusion of this study: The degree of sustainable intensification of farmland use is influenced by climate change, the use of agricultural machinery and equipment, the amounts of chemical fertilizers and pesticides used, and cultivation methods. Therefore, the use of farmland requires a rational allocation of emergy inputs within the socio-economic system, coupled with the scientific maximization of outputs while maintaining the ecological and economic integrity of farmland. This approach is of great importance as a reference for the efficient use of farmland resources in China and thus for national food security. Additionally, this research provides valuable insights that can serve as a useful reference for other regions worldwide.
