Relationships between darkening of dried apricots and nutrient concentrations in fresh fruit and mid-shoot leaves

Abstract

Relationships between darkening of dried apricots in storage and nutrient concentrations in mid-shoot leaves and fresh fruit collected at harvest were studied. Commercial orchards were sampled for 3 growing seasons throughout the irrigation districts of Berri, Loxton and Renmark in South Australia. Darkening of dried apricots was assessed as the time taken for the optical absorbance of 50% ethanolic extracts of the dried fruit to reach 0.3, hereafter referred to as weeks to OD 0.3. Linear or quadratic relationships were found between weeks to OD 0.3 and (i) nitrogen, calcium, magnesium, sodium, chloride, sulfur, boron and copper concentrations in both leaves and fresh fruit; (ii) potassium and iron concentrations in leaves; and (iii) phosphorus and manganese concentrations infresh fruit. However, for nutrients other than nitrogen, relationships were not found consistently in each of the 3 growing seasons. Further, although statistically significant, the relationships were of little predictive value, with coefficients of determination (r ² ) as low as 0.03. Coefficients of determination for the relationships between weeks to OD 0.3 and nitrogen concentrations in fresh fruit, were 0.73 in 1992–93, 0.20 in 1993–94, 0.51 in 1994–95 and 0.61 for the 3 seasons’ data combined (1993–95). It is suggested that nitrogen concentration in fruit at harvest is a useful tool to predict the darkening of dried apricots during storage.