Effects of foliar spray of different Fe sources on pepper (Capsicum annum L.) plants in aquaponic system

An experiment was carried out to investigate the effects of foliar applications of different Fe sources on pepper plants grown in alkaline aquaponic solutions. Common carp was stocked in the rearing tanks at 50 fish m−3. The fish were fed three times daily with a pellet diet containing 46% protein. Twenty days old pepper seedlings were transplanted on to growth bed units of aquaponic system after stocking of carp fish for 2 months in the rearing tanks. Foliar nutrients application began 30 days after transplantation. Four treatments were used, untreated control, foliar application at the rate of 200 mL plant−1 with 0.5 g Fe L−1 FeSO4, Fe-EDTA, and Fe-EDDHA. Plants were sprayed twice a month. The results showed that overall growth was significantly increased by foliar Fe application, and the highest values of vegetative and reproductive growth parameters were recorded in plants treated with FeSO4. The lowest chlorophyll content was observed in untreated plants. The highest SPAD index, maximal quantum yield of PS II photochemistry (Fv/Fm) and performance index (PI) values of young and old leaves were found with FeSO4, with no difference between Fe-EDTA and Fe-EDDHA treatments. The Fe treatment led to a significant increase of shoot Fe concentration in pepper plants, so that the highest shoot Fe concentration was observed in plants sprayed with Fe-sulfate, whereas Fe-EDTA and Fe-EDDHA led to intermediate concentrations and control led to the lowest one. Foliar fertilization of pepper plants with different Fe sources had a beneficial effect on the essential nutrient uptake and transport in plants. Thus, present results revealed that application of foliar Fe must be performed in the aquaponic system, to overcome Fe deficiencies in alkaline conditions and to make better nutritional status.

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► Different Fe sources were sprayed on pepper plants in aquaponics.
► Overall growth was increased by foliar Fe application.
► The lowest Fe and chlorophyll content were observed in control (untreated) plants.
► The highest Fe, SPAD index, Fv/Fm, and PI values in leaves were found with FeSO4.
► Fe-EDTA and Fe-EDDHA led to intermediate concentrations of Fe in the leaves.