This study was conducted during two successive seasons of 2013/2014 and 2014/ 2015 on 15-year-old Washington navel and Valencia orange [Citrus sinensis (L.) Osbeck] trees grafted on sour orange rootstock. The experimental trees were grown in clay loam soil of a private citrus orchard located at Menia El-Kamh district, Sharkia Governorate, Egypt. Fruits were harvested at 5 successive monthly intervals on the first of each of Dec., Jan., Feb., Mar. and Apr. for Washington navel orange. Valencia orange fruits were harvested one month later at five periods beginning with first Jan. and ending with first May. On each harvest date fruits of three trees (3 replicates) were harvested, counted and weighed. About 60 healthy undamaged fruits from each replicate were randomly selected for cold storage at 7ºC±1 and 85-90% RH. Fruit samples selected at harvest day (15 fruits) and those taken at 30 days intervals from cold stored fruits were subjected to determine the effect of on-tree, cold storage and harvest date on physicochemical fruit characteristics. Washington navel orange gained the highest fruit weight, TSS/acid ratio, fruit weight loss and fruit decay percentages, whereas, Valencia orange produced higher fruit yields with higher vit. C content. Yield/ tree, fruit weight, TSS/ acid ratio and vit. C content were markedly decreased by delaying fruit harvest (on-trees fruits storage) and increasing storage period, but weight loss and decay percentages were increased. All possible interactions between the three tested factors were significant in the two seasons, and confirm the previously recorded trends of each individual factor on the tested physicochemical fruit characteristics. The obtained results revealed that the storability of Valencia orange fruits was clearly better than that of Washington navel orange fruits, since weight loss and decay percentages of the later orange variety were about 2 and 15 folds than that of Valencia orange fruit, respectively (average of both seasons).
Mandarin ‘Murcott’ (Citrus reticulata Blanco) trees aged five years that were grafted onto lemon ‘Volkamer’ (Citrus volkameriana) rootstock and grown in sandy soil under a drip irrigation system were used in this study during the growing seasons of 2018 and 2019. Ten different fertilization treatments combining inorganic, organic, and biofertilization in a completely randomized block were performed. The results revealed that fertilizing ‘Murcott’ mandarin trees with 75% of the recommended dose (RD) of nitrogen as inorganic nitrogen (33.5% N) in the form of NH4NO3 + 25% of RD as organic nitrogen in the form of chicken manure (3% N) per tree per year without or with a biofertilizer (Effective Microorganisms, EM1) at 150 mL/tree increased the weight, size, pulp, and peels of mandarin fruit, as well as the fruit juice volume, juice volume/fruit, and vitamin C, but reduced the total acidity in both seasons. However, fertilizing ‘Murcott’ mandarin trees with 100% of RD as inorganic nitrogen increased the pulp/fruit ratio, and fertilizing with 25% of RD as inorganic nitrogen + 75% of RD as organic nitrogen + biofertilizer EM1 increased the peel/fruit ratio, peel thickness, and fruit firmness. Fertilizing ‘Murcott’ mandarin trees with 100% organic nitrogen + biofertilizer EM1 increased total soluble solids (TSS) and total sugar contents while producing the lowest nitrate (NO3) percentage in ‘Murcott’ mandarin fruit compared with trees fertilized with inorganic nitrogen only. The fruit produced by ‘Murcott’ mandarin trees fertilized with 100% of RD as organic nitrogen with or without biofertilizer EM1 contained higher TSS, total carbohydrates, and sugars and lower nitrate percentages than those fertilized with inorganic nitrogen and biofertilizer EM1. This study contributes to reducing the use of inorganic fertilizers by adding a percentage of an organic fertilizer to obtain a healthy product that contains a lower percentage of NO3, which affects the health of the consumer, and is of high quality and suitable for export.
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