There are important advantages in being able to make a prediction of storage quality early in fruit development as opposed to harvest time. Early prediction allows growers more time to plan and organise their storage and marketing schedule and, where possible, apply remedial measures to correct specific nutrient deficiencies.
Previous studies on Cox showed that the ability to predict ex-store firmness or storage disorders such as bitter pit based on mineral analysis alone declined when samples were analysed in mid-July or early August as opposed to late August or at harvest.
However, recent work has indicated the possibility of predicting mineral concentrations in the fruit at harvest on the basis of fruitlet composition and weight and an expected weight of fruit at harvest. Good correlations have been achieved for fruitlet calcium and bitter pit development under New Zealand conditions.
In the North America ‘Fruitlet Guide’ ranges are provided with test results for early season fruitlet analysis so that growers can diagnose deficiencies relatively early in the growing season. However, this programme recommends a further analysis of fruit just prior to harvest. These predictions are based on the general inverse relationship between mean weight per apple and mean calcium concentration.
There is insufficient storage quality and mineral analysis data to establish mineral threshold concentrations for cultivars such as Gala and Braeburn that are increasingly important in UK production. Experiments to provide this information would need to be extended over a number of years in order to allow for the marked seasonal effects on storage quality.