Link
Publication
- Journal: Agronomy, Vol. 15, No. 10, 2438 (2025)
- Authors: Mi Young Lim, Dongpil Kim, Se Jin Kim, Gyeong Lee Choi, Mi Young Rho, Hee Sung Hwang
- DOI: 10.3390/agronomy15102438
- Open Access: CC BY 4.0
Summary
Closed (recirculating) hydroponics saves water and fertilizer, but growers worry that reusing the solution unbalances its ions and destabilizes yield. We tested that concern in a commercial tomato greenhouse by continuously monitoring drainage from an open (non-recirculating) system and a closed system. EC, pH and the major ions (NO₃⁻, K⁺, Ca²⁺, Mg²⁺, SO₄²⁻, PO₄³⁻ and Na⁺) were measured by ion chromatography. Guided by the ion trends, we compared nutrient compensation every 0, 2 and 4 weeks in the closed system.
Key Findings
- Ionic imbalance: Contrary to growers' expectations, the open system showed the larger ionic imbalance, driven by uncontrolled leaching.
- Compensation interval: In the closed system, compensating every 4 weeks was enough to keep ion ratios stable.
- Resource savings: Compared with the open system, fertilizer input fell by 67–69% and water use by 33–36%.
- Implication: Drainage ion monitoring combined with periodic compensation improves both the environmental and economic performance of closed hydroponics.