Closed-Loop Crop Cascade to Optimize Nutrient Flows and Grow Low-Impact Vegetables in Cities

Urban Farm DB summary

This study investigated a closed-loop crop cascade system in a Barcelona rooftop greenhouse, using tomato leachates to irrigate five successive lettuce cycles. The results showed that low yields (below 130 g per lettuce plant) were obtained when the cascade system was used during the early stage of the donor crop, as the nutrient amount, especially nitrogen, was insufficient for the receiving lettuce crop. Additionally, electrical conductivity values became too high (near 3 dS/m) at the end of the donor crop cycle, indicating limitations in maintaining optimal conditions throughout.