In this study, we evaluated the effect of various fertilization regimes on processing tomato (Solanum lycopersicum
L. cv. Heinz 3402) yield and quality by applying the following treatments: (i) control (C), (ii) conventional fertilizer (21-0-0, N-P-K) (CF), (iii) slow release nitrogen fertilizer 46-0-0 (SR), (iv) conventional fertilizer (21-0-0, N-P-K) + Zeolite (CFZ), and v) composted sheep manure (M). The results of the study showed that the SR and CFZ treatments resulted in the highest fruit yield per hectare compared to the rest of the fertilizer and the control treatments. Fruit firmness was higher for the treatments C, M and SR, while color parameters (chroma and hue angle) were higher for the C and M treatments, respectively. Moreover, the total soluble solids content (TSS; °Brix) was higher when manure (M) was applied. In terms of chemical composition, the total and individual tocopherols and sugars were the highest for the M and C treatments, respectively, whereas the oxalic, malic and total organic acid contents were the highest for the CFZ treatment. Moreover, the tested treatments showed a varied response in different antioxidant assays, although the M treatment exhibited a high antioxidant capacity in most of the assays, except for the β-carotene/linoleate assay. The carotenoid and chlorophyll contents were the highest for the control treatment. The main detected fatty acid was linoleic acid, followed by palmitic, oleic and α-linolenic acid, while the CFZ treatment had the highest content of polyunsaturated fatty acids (PUFA) due to its high content of linoleic acid. In conclusion, although the application of fertilizers increased yield, the quality parameters and chemical composition showed a varied response to the fertilization regime, especially the TSS content and juice pH and electric conductivity (EC), which are significant for the marketability of the final product.
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