How to manage stone fruit firmness

Excessive thinning of fruit can result in a higher number of cells per fruit, increasing firmness in the remaining crop. Proper crop nutrition also helps to achieve adequate firmness levels.

Minimum fruit firmness standards have been established for different stone fruit types. These are measured by penetrometer, which determines the pressure needed to push a plunger of specific size to a specific depth within the pulp of the fruit.

Crop Nutrition and Stone Fruit Firmness

Calcium

Fruits with high levels of calcium are firmer. The skin and flesh is less liable to breakdown disorders with reduced leakage through cell wall membranes. Thus, good calcium supply delays ripening and increases storability of fruits. Best responses come from a spray programme aimed at the fruit. The rate and number of application is important.

Calcium Nitrate has provided better responses in trials than calcium chloride. However, soil applied calcium also has a positive effect on fruit firmness.

Provided adequate supplies of calcium are maintained, high levels of magnesium will also improve fruit firmness.

Copper

Copper has a positive effect on fruit firmness, as you can see in the graph.

Nitrogen

Too much nitrogen decreases fruit firmness making the fruits more susceptible to diseases such as split-pit on peaches

Too much nitrogen decreases fruit firmness making the fruits more susceptible to diseases such as split-pit on peaches.