NIRS as a tool for precision horticulture in the citrus industry

Near-infrared spectroscopy was applied for non-destructively monitoring the soluble solids content of citrus fruit on trees. The model was built on refractometer readings and NIR spectra from outdoor measurements of fruit corrected for the ambient light conditions. The model was not significantly influenced by the variations in fruit temperature. The results showed that a high precipitation rate had a severe impact on the fruit quality. The average development of the cultivar-specific harvest date was used as a reference to calculate the relative harvest date of individual fruit indicating how non-destructive sensors could be integrated within the framework of precision horticulture.