Plant nutrient uptake in recirculation culture of tomato under growth stage based electrical conductivity adjustments

* Corresponding author ([email protected]) Abstract: Recirculation (closed) type hydroponics, despite its comparative eco-friendliness and cost-effectiveness, is less popular in greenhouse agriculture due to the need for close monitoring of nutrient availability within the fertigation cycle. As a practicable and low cost measure, the uptake volume based supplementation of plant nutrients at high concentrations was studied in tomato (Solanum lycopersicum L.) plants at different stages of maturity using the nutrient film technique (NFT). The plants of four age groups or maturity stages (MS), 5, 4, 3 and 2 weeks old at transplanting (MS1, MS2, MS3 and MS4, respectively), were grown in a complete hydroponic solution (Enshi), keeping the electrical conductivity (EC) set-point at 1.8 dS m. EC of the stock solution was maintained at 1.6 dS m until the flowering stage and then changed to 1.1, 1.2, 1.6 and 1.7 dS m in treatments MS1 through MS4 respectively. Young leaves were removed in MS1 while old leaves were removed in MS4 during the last two weeks to create substantially different nutrient demands among the MS treatments. The depleted volume of the supply solution was supplemented daily during the 1-2 week recirculation cycles. EC of the supply solution was monitored and the pH was adjusted to 6.5 daily.