Postharvest Quality of Sweet Orange Fruits in response to Soil Amendments and Harvest time in South Western Nigeria
Nutrient management in sweet orange production has tremendous effects on fruit quality at the time of harvest. Two research trials were conducted between 2016 and 2017 production seasons to determine the effects of soil amendment and time of harvest on the physicochemical properties of sweet orange fruits at maturity. Sweet orange trees were selected from an orchard managed under organic practices at the Federal University of Agriculture, Abeokuta, Nigeria. The soils were amended with poultry manure (PM) at: 0, 5, 10 and 15 t ha-1 in September, 2016 and March, 2017 at flowering stages. Physiologically- matured fruits
were harvested during the first harvest season (March - April, 2017) and also during the second harvest season (August - September, 2017). Soil amendment of plants that received 10 t ha-1 PM produced fruits with significantly higher amount of total soluble solids (TSS) with reduced titratable acidity while fruits produced from plants fertilized with 15 t ha-1 had increased fruit weight, juice volume and vitamin C contents relative to fruits produced from plants that received 0 and 5 t ha-1 from first and second harvests. The lightness(L*) and yellowness (b*) values in peel colour of fruits harvested from plants that received 10 t ha-1 was improved compared with fruits that received 0 t ha-1 PM. Application of different rates of PM had no significant effects on juice colour of harvested fruits. Fruits from the first harvest had increased TSS values with reduced titratable acidity while fruits from second harvest had increased fruit weight, juice volume, vitamin C and L* in the juice colour. Sweet orange plants fertilized with 10 t ha-1 PM produced sweeter fruits while application of 15 t ha-1 PM produced
heavier fruits with increased vitamin C and juice contents at first and second harvests.