Fulvic acid has been considered as a valuable fertilizer for sustainable agriculture. The present investigation was undertaken to evaluate the effect of fulvic acid (FA) on antioxidant compounds and fruit quality of pepper under field conditions. Plants were grown in the Department of Horticulture Farm, Ferdowsi University of Mashhad, Iran (latitude 36° 17′ N, longitude 59° 35′ E and 985 m elevation). The experiment was designed in randomized block design with three replications. Treatments consisted of five levels of fulvic acid (0, 25, 100, 175 and 250 mg kg-1). The results indicate that fruit antioxidant activity, total phenolic, carbohydrate, capsaicin and carotenoids contents were influenced by fulvic acid, but total flavonoid and ascorbic acid contents were not affected significantly by fulvic acid treatments applications. FA applied at 25 mg kg-1 resulted in the highest carbohydrate content, lycopene and β-carotene contents, while the lowest values were recorded in the control. Fulvic acid treatments positively affected fruit quality (total soluble solids and titratable acidity); total soluble solids and titratable acidity significantly increased in response to FA treatments. These results confirm that the use of fulvic acid have a positive effect on antioxidant activity and quality of hot pepper under field conditions.

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