Nitrogen fertilisation on peach trees: effect on nutritional status, yield and susceptibility to Phomopsis amigdali

Doutoramento em Engenharia Agronómica - Instituto Superior de AgronomiaThe area of peach trees, in Beira Interior region, covers 25% of the Portuguese total area of peach trees, being 64% of the orchards located in distric cambisols and 30% in distric fluvisols, with an average size of 7.6 ha per grower. In potted plant and field trials, the effect of nitrogen fertilisation on peach tree nutritional status, vigour, yield, fruit quality, susceptibility to Phomopsis amygdali, and presence of insects like Anarsia lineatella, scolitydae, and aphids was studied. The nitrogen fertilisation showed effects on the nutritional status and vegetative growth, but in the field trial there were no significant effects on total yield (19 to 30 t.ha-1), commercial yield (16 to 28 t.ha-1), and fruit size. The Multiple Correspondence Analysis allowed us to identify that susceptibility to peach constriction canker was changed by rainfall and leaf nitrogen content, showing higher susceptibility the plants with higher nitrogen fertilisation in high rainfall conditions, but the nitrogen effect was not so striking in low rainfall conditions. In Rich Lady peach commercial orchards, there was a close association between canker susceptibility, plant age, and leaf nitrogen contents; high levels of canker incidence associated with older orchards and high leaf nitrogen content were detected; the nitrogen effect was not so evident when plants were younger