Effet du digestat à base de Tithonia diversifolia et de bouse de vache sur les paramètres de croissance et la qualité nutritionnelle de la carotte (Daucus carota)

Abstract

The present study aimed to evaluate the effect of digestate based on Tithonia diversifolia and cow dung on the agro-morphological parameters and the sensory and nutritional qualities of carrots in order to contribute to the improvement of production yields and the nutritional quality of foodstuffs. To achieve this objective, carrot seeds were treated with Tithonia diversifolia extract 2%. An experimental design in randomized complete blocks with three blocks partitioned into plots on which the carrot seedlings were planted. The 8 treatments applied consisted of a single soil amendment with solid digestates (T20, T50, T80, T100) and T. diversifolia compost and spraying every two weeks after amendments of the plants with liquid digestates or compost juice from the same fertilizers. After 120 days of culture eight batches of plants (T0, TN, TC, TVC, T20, T50, T80, T100) were obtained. Agro-morphological parameters, post-harvest conservation were evaluated by conventional methods, chemical analyzes (sugars, proteins, fibers) were carried out by standard AOAC, AFNOR methods; titrimetry for vitamin C; spectrophotometry for total carotenoids and by atomic absorption spectrophotometry for minerals. Phenolic compounds and antioxidant power (DPPH test) by conventional methods. The sensory analysis of carrots was carried out by a 9-level hedonic test with 61 untrained panelists. Of the results of general acceptability, the T100 carrots were the most appreciated by the panelists. Thus post-harvest storage varied at intervals of 3 to 5 and 24 to 26 days (room temperature) and 60 to 70 and 105-115 days (4°C) for carrots from control and biological treatments respectively. The protein, total sugar and crude fiber contents of carrots are respectively between 7.84±0.02 and 11.00±0.00 g/100g DM; 21.56±0.84 and 154.95±0.70g/100g DM; 6.81±0.09 and 10.50±0.21 g/100g MS. With regard to vitamin C, the levels vary from 42.24±0.38 to 134.57±0.24 mg/100g DM. The total carotenoid contents oscillated respectively between 7.92±0.02 and 16.50±0.02 mg/100g DM. The results of this study showed that the use of organic inputs improved agronomic parameters, shelf life, nutrient content and antioxidant power. From the above, T. diversifolia-based fertilizers are good candidates for organic carrot cultivation.