Effects of Organic and Mineral Fertilizers on total Antioxidant, polyphenolic and carotenoid contents of Orange fleshed sweetpotato tubers

Abstract

Abstract

A field study was conducted to determine the effect of organic and mineral-based fertilizers on phytochemical contents in the tubers of an orange fleshed sweetpotato variety (TIB-440060). Treatments were arranged in a split plot design with three replicates. Tubers harvested have been studied for their total antioxidant contents (TAC), total polyphenolic contents (TPC) and total carotenoid contents (TCC) using Ferric Reducing Antioxidant Power (FRAP), Folin-Ciocalteu reagent (FCR) and a method described by McMurry respectively.

Organic fertilizer had a positive effect on the production of antioxidants, polyphenols and carotenoids whose contents increased significantly (P < 0.001) with the quantities of organic fertilizer. Increases about 19.61%, 34.41% and 12.82% due to annual (F1) inputs and increases about 15.94% and 15.46% and 12.17% respectively in total antioxidant, polyphenolic and carotenoid contents when these inputs of organic fertilizer are conducted biennially  (F2).

The effect of different doses of mineral fertilizers indicated significant changes (P < 0.001) in accumulated antioxidant, polyphenolic and total carotenoids contents of TIB-440060 OFSP tubers.

Total Antioxidant, polyphenolic and carotenoid contents of TIB-440060 varied significantly (P < 0.001) with the combination of organo-mineral fertilization used. Combinations using a minimal doses of 15 kg/ha of nitrogen, 30 kg/ha phosphorus and 45 kg/ha of potassium associated with an annual or biennial contribution of 20 t/ha of organic fertilizer gave the highest total antioxidant, polyphenolic and carotenoid concentrations.

Keywords: OFSP extracts, phytochemical contents, polyphénols, antioxidants, carotenoids, organic fertilizer, mineral fertilizers, FRAP, FCR