Emergy analysis of grain production systems on large-scale farms in the North China Plain based on LCA
Traditionally, primary grain production systems in China have been on a small scale and are associated with high costs and low labor productivity. Therefore, the substitution of small-scale farming with large-scale farming has been discussed in recent years. The North China Plain (NCP) is one of the primary grain production areas in China, and the winter wheat–summer maize double-cropping system dominates the region. Emergy evaluation based on life cycle assessment (LCA) was introduced in a farm case study to explore the ecological and economic effects of the wheat–maize double-cropping system on large-scale grain production compared with small-scale production. The results indicated that the emergy efficiency of maize production on the large-scale farm was 67.4–88.5% higher than that of common maize production systems, and the emergy efficiency of wheat production in the same farm decreased by 23.5–43.0% compared to other wheat production systems. The emergy sustainability index (ESI) of the double-cropping system was 64.0–84.5% lower than that reported by household farms. This is caused by large-scale farming requiring enormous emergy inputs from irrigation, fertilizers, and labor at the pre-sowing and growth stages of wheat production. Nevertheless, the scenario analysis results showed that the emergy efficiency and ESI of wheat production could be improved by 14.7–59.1% and 18.2–123.3%, respectively, using appropriate water, nutrient, and agronomic management measures. We found that the emergy efficiency of wheat production in this large-scale farm was 41.5% higher than in household farms in the same area if comprehensive improvement measures were applied. In conclusion, the ESI value of the double-cropping system in the NCP needs to be modified to increase the emergy efficiency of large-scale grain production farms. If this is accomplished, the large-scale farming pattern may be applicable for grain production in the NCP.
