Cascade cropping for enhancing environmental footprint: a case study of rocket salad production
摘要
Cascade cropping is a type of closed-loop soilless system where effluent from a primary crop is used to irrigate a more salt-tolerant secondary crop, and the growing medium can be reused in subsequent cultivation cycles. This approach has emerged as a promising strategy to optimize nutrient use efficiency and mitigate leaching-related environmental pollution. This study assesses the effectiveness of cascade cropping in enhancing environmental sustainability compared to conventional soil and soilless cultivation. The case study is rocket salad cultivation, with glasswort as a secondary crop in the cascade system. A cradle-to-farm-gate life cycle assessment was performed according to the ISO 14040/44 standards to study nine midpoint impact categories recommended by the European Commission’s Product Environmental Footprint Category Rules. The results show that the cascade system significantly outperformed conventional cultivation across most environmental impact indicators, particularly when incorporating locally produced compost into the growing medium. The following impact reductions were achieved compared to the soil and soilless systems respectively: 38% and 79% in global warming; 58% and 75% in fossil resource scarcity; 55% and 99% in freshwater eutrophication; 95% and 98% in marine eutrophication; and 62% and 82% in water consumption. However, the cascade system doubled the impact on the human carcinogenic toxicity category, since this category is dominated by infrastructure and the cascade system had a higher demand for material extraction and manufacturing. These findings highlight the potential benefits and trade-offs of cascade systems and underscore the importance of designing resource-efficient systems.