Effects of foliar application of some macro- and micro-nutrients on tomato plants in aquaponic and hydroponic systems

An aquaponic system was designed to investigate effects of foliar applications of some micro- and macro-nutrients on tomato growth and yield in comparison with a hydroponic system. Common carp, grass carp and silver carp were stocked in the rearing tanks at 15, 20 and 15 fish m⁻³, respectively. The fish were fed three times daily with a pellet diet containing 46% protein. Fourteen days old tomatoes seedlings were transplanted on to growth bed units of aquaponic and hydroponic systems after stocking of carp fish for 2.5 months in the rearing tanks. Foliar nutrients application began 30 days after transplantation. Eight treatments were used, untreated control, foliar application at the rate of 250 mL plant⁻¹ with 0.5 g L⁻¹ K₂SO₄, MgSO₄·7H₂O, Fe-EDDHA, MnSO₄·H₂O, H₃BO₃, ZnCl₂, and CuSO₄·5H₂O. Plants were sprayed twice a month. The results showed that biomass gains of tomatoes were higher in hydroponics as compared to aquaponics. Foliar application of K, Mg, Fe, Mn, and B increased vegetative growth of plants in the aquaponics. In the hydroponics, only Fe and B had positive effects on plant growth. Cluster number per plant in aquaponics was lower than in hydroponics treatments, but it increased with foliar application of elements. There was no difference in fruit number and yield between aquaponics and hydroponics grown plants in the control treatments. Except Cu, foliar spray of all elements significantly increased plant fruit number and yield in the aquaponics in order of: K > Fe > Mn > Zn > Mg > B. In the hydroponics, foliar application of K, Mg and Zn increased fruit number and yield of plants compared to control. These results indicated that foliar application of some elements can effectively alleviate nutrient deficiencies in tomatoes grown on aquaponics.