Nitrogen fertilization and orchard-floor vegetation management affect growth, nutrition and fruit quality of Gala apple

Gala apple (Malus × domestica Borkh) trees on M.26 rootstock planted in 1989, were subjected to a factorial combination of treatments involving two N fertilizations (N1 and N2) and two orchard-floor vegetation-management treatments (V1 and V2), 1990–1995. Single annual, spring-broadcast application of N at 80 kg ha−1 were made at N1, while N2-treatments involved split N applications of either 2 × 100 kg ha−1 (1990–1993) or 3 × 80 kg ha−1 (1994–1995). Herbicide strips (1.5-m width) were maintained free of orchard-floor vegetation year-round (V1) or annually until mid-July (V2). The high N regime (N2) increased leaf and fruit N concentration and decreased fruit P and leaf and fruit K concentrations but had few negative effects on fruit quality, decreasing harvest fruit ground red color in 2 yr and firmness in a single year and titratable acidity of stored fruit in 2 yr. Increased tree yield was measured at N2 only in 1995. Greater vegetation competition in the V2 treatment decreased yield in 1991–1992 and cumulative yield for 1991–1995 but had few effects on leaf and fruit N concentrations. Leaf and fruit K concentrations were generally increased at V2 as was titratable acidity of stored fruit. Fruit from V2 treatments had increased red ground color (2 yr) and increased firmness at harvest (3 yr) or after storage (2 yr) but decreased soluble solids at harvest (2 yr). Fruit was free of disorders and had a high Ca concentration regardless of treatment or year implying Gala apple is a good Ca accumulator. Key words: Malus × domestica, leaf and fruit N, P and K, fruit Ca, yield, fruit firmness