Calcium to combat post-harvest disorders

30 September 2016 | Dean Rainham, AgFirst | Australian Fruitgrower article

Calcium status is a key part of managing post-harvest disorders such as bitter pit and blotch. This Future Orchards® article explains how calcium availability in the soil, root activity, irrigation, tree vigour, crop load and nutrient balance combine to determine how much calcium reaches developing apple fruit.

Calcium moves primarily in the transpiration stream and fruit uptake is strongest during roughly the first six weeks after fruit set. Because calcium does not readily redistribute from leaves to fruit later in the season, the article stresses the value of maintaining healthy roots and even soil moisture early, then using foliar calcium sprays to keep supplying expanding fruit as the season progresses.

Risk is higher where crop load is light, fruit are large, vigour is excessive, blocks have a history of low fruit calcium, conditions are hot and dry, or nitrogen, potassium and magnesium are out of balance. Management therefore needs to be coordinated across pruning, crop loading, irrigation, root health, nutrition and spray programs rather than relying on a single calcium input.

For pit-sensitive varieties, the article recommends a disciplined, season-long calcium program alongside monitoring of soil pH, soil and leaf nutrient balance and block history. The core message is that good post-harvest quality is built through whole-tree management well before fruit enters storage.