Effect of foliar application of potassium with aquaculture wastewater on the growth of okra (Abelmoschus esculentus) and Pangasianodon hypophthalmus in recirculating aquaponic system

A 90-day experimental trial was conducted to evaluate the effect of foliar potassium application with aquaculture wastewater on the growth performance of okra and Pangasianodon hypophthalmus in a media-based recirculating aquaponic system. A completely randomized design (CRD) in triplicates was followed with a fish to plant ratio of 4.7 kg/m³: 6 okra plants per tank. The potassium dosages of 0, 2, 3, 4, and 5 g/L were applied twice a month in control, T1, T2, T3, and T4, respectively. The water quality parameters remained within the favorable limit for aquaponic production. The results showed that the overall growth of okra viz., plant height, leaf number, length, and width was significantly higher in the treatments, particularly in T3 and T4 compared to other treatments and the control. The treatment T4 showed the significantly highest yield (31.26±0.78 g/plant) compared to the control (7.25±1.30 g/plant). The okra yield, pod number per plant, and average weight per pod were significantly influenced by potassium dosage with the highest value observed in T3 (4 g/L) and T4 (5 g/L). The potassium dosage also impacted the branching pattern of okra with the highest number of branches observed in plants sprayed with 4 g/L (T3) and 5 g/L (T4) while control showed no branching. The proximate and mineral composition showed significantly higher crude protein (13.57±0.32%) and potassium content (2306.70±37.76 mg/100 g) in okra pods in T4; while potassium and sulfur content of leaves was found to increase with the increased dosage of potassium application. The fish growth, hematological and antioxidant enzymes parameters showed no significant difference in all the treatments and control. The present study recommends a 5 g/L foliar potassium dosage to enhance okra growth and yield without impairing fish growth performance in okra-P. hypophthalmus aquaponics.