How to increase apple firmness

Nitrogen excess can reduce apple firmness

Over-use or late applications of nitrogen reduces apple firmness, potentially resulting in more damage in transit and storage, and a reduced shelf life.

Phosphorus can improve long term storage

Calcium has a major role in producing firm fruit

Calcium has a major role to play in maximizing apple quality by providing firm fruit. Cell wall integrity and cell-to-cell adhesion is improved, resulting in a tougher flesh that is less prone to bruising or tissue breakdown.

Soil applied calcium nitrate is very effective in improving fruit firmness. When using foliar applications, the more sprays the better, provided that products such as calcium nitrate don’t deliver too much nitrogen, creating nutrient imbalances and loss in quality. 

Trials suggest that for firmness, the critical value of calcium in apple at harvest is higher than the 5mg/100g fresh weight recommended for minimizing bitter pit.