Partial Recirculation in Two-Tier Indoor Aeroponic Strawberry: Yield-Input Trade-Off and Nutrient-Solution Drift

Partial recirculation can reduce water and fertilizer inputs in indoor strawberry production, but excessive reuse may cause ion-specific nutrient-solution drift. We compared 0%, 30%, and 50% recirculation of gross supplied water in a closed two-tier indoor aeroponic system for ‘Seolhyang’ strawberry over two cultivation years. Each treatment was evaluated as a descriptive operational comparison across the cultivation years, with no independent block-level replication within each cycle. Each recorded run represented directly measured harvest from three internal blocks (480 plants; 25 m2), converted to per-block values (160 plants; 8.33 m2). All the treatments used a stage-adjusted Yamazaki-based nutrient solution, common EC/pH targets, and a gross irrigation supply of 54.0 m3 cycle−1 for the three-block run. Return-water chemistry was analyzed biweekly. Mean yield was 71.7 kg block−1 in the non-recirculating control, 70.0 kg block−1 at 30% recirculation, and 41.7 kg block−1 at 50% recirculation, equivalent to 0.45, 0.44, and 0.26 kg plant−1. Fresh make-up water demand was 18.0, 12.6, and 9.0 m3 block−1 cycle−1, respectively. Increasing reuse depleted P and K; accumulated Ca, Mg, and Na; and narrowed K:Ca and K:(Ca+Mg) ratios. Our results establish 30% recirculation as the threshold that maximizes resource recovery without compromising yield.