HARVEST AND POSTHARVEST APPLE QUALITY INFLUENCED BY BORON APPLICATION

The effect of boron fertilizing was studied on 8 apple cultivars by using an experimental fertilizer, named urea-boron (20.0.0 + 7B₂O₃), applied yearly in the period 1985–87. The experiments, carried out in 2 different pedo-climatic environments, that is Ravenna (plain) and Pavia (hill), compared the following fertilizing trials:

• Ravenna 50 kg/ha of N (urea) in autumn or spring,
• Ravenna 50 kg/ha of N (urea) +17.5 kg/ha of B₂O₃ in autumn or spring,
• Pavia 100 kg/ha of N (urea) in spring,
• Pavia 100 kg/ha of N (urea) +34 kg/ha of B₂O₃ in spring.

At harvesting, observations were made on apple production, bitter pit incidence and fruit peculiarities. The 2 last ones were also registered after 5 months of storage in cooling chambers with a normal atmosphere. Besides, during the whole vegetative season, leaf mineral element content was examined making 4 samplings yearly. In these trials the results obtained for the fertilizing test with urea and boron, with the test applying only urea, were as follows:

• a significant bitter pit decrease at harvest and after storage, above all in the orchards of Pavia, where the incidence of this physiological disorder was greater;
• normal or good qualitative properties of fruits at harvest and after cold storage;
• a bigger leaf aboundance of mineral elements in the trials with boron, above all as for calcium is concerned;
• a no significant influence on productivity.

Fertilizing period seems to have no significant influence. Further investigations are nevertheless necessary as to evaluate particularly the effect of a boron fertilizing as years go by.