The influence of various levels of ammonium to total nitrogen on post-harvest performance of three apple cultivars (Golab Kohans, Gala, and Granny Smith)

Apple is one of the most popular fruit worldwide with a continuous demand for higher quality apples, especially storable varieties. Nitrogen is one of the most important elements in apple growth and production. Additionally, different nitrogen forms can have different effects on plant growth and fruit qualities. In this research, we investigated the effect of five types of nutrient solutions with different amounts of ammonium nitrogen to total nitrogen on post-harvest physiology of apples for two seasons (2016-2017 and 2017-2018). Apple seedlings of three cultivars (Granny Smith, Gala and Golab Kohans) were grown on a soil-based substrate in a factorial experiment of randomized complete block design. After harvesting, the fruit were stored in 0 ○C and 90-95% humidity for 45 days for Golab, 90 days for Gala and 160 days for Granny Smith. Fruit traits were evaluated throughout storage period. The results showed that the increase in ammonium nitrate concentration significantly increased fruit weight, fruit dry weight, and titratable acidity. However, this increase in ammonium nitrate reduced firmness and the amount of total soluble solids with an increase in fruit weight loss index during storage. Furthermore, the results illustrated that the best fruit in terms of storability and postharvest performance were attributed to the nutrition solution without ammonium nitrate.