Designing productive, energy-efficient, and environmentally friendly production systems by replacing fallow period with annual forage cultivation on the Loess Plateau of China

Intensifying agriculture to meet the food requirements of the growing population could result in increased energy demands and production costs with accompanying environmental hazards such as greenhouse gas emissions. There is a need to develop environmentally friendly and economically viable cropping systems to maintain sustainable agriculture and livestock production. A 4-year field experiment (2015-2019) was conducted to investigate the energy requirements, energy efficiency, economic returns, and greenhouse gas emissions (GHGs) of six crop rotation systems. These crop rotations were established by intensifying the traditional winter wheat (Triticum aestivum L.) mono-cropping and winter wheat-maize (Zea mays L.) cropping rotation systems with forage rape (Brassica napus L.) or common vetch (Vicia sativa L.). The results showed that the average system ecoefficiency index (EEI) decreased by 63.0% and that GHGs increased by 43.3% when traditional cropping systems were intensified with forage rape. Compared to the rotations that included forage rape, the rotation with common vetch had a 67.5% higher average EEI and an 85.3% higher energy efficiency. Replacing the summer fallow period with common vetch increased the average economic return and forage yield by 22.9% and 4.41 t ha-1. The results suggested that planting common vetch during the summer fallow period may be a productive and economically sound practice that has low energy requirements. This practice could benefit agriculture by providing cleaner, more energy-efficient production under a scenario of global environmental pollution and constrained resources. Crop selection by farmers that is based on energy requirements they relate to crop market values and GHGs is crucial for the profitability and eco-efficient incorporation of forage crops into cropping systems. Further study to include other important factors such as acidification and eutrophication is recommended for a comprehensive evaluations of environmentally friendly production systems.