Tree vigour and yield of plum grown under high density planting system

Abstract

During the second through sixth growing seasons, under the environmental conditions of Cacak (Serbia), tree vigour, yield (kg tree-1 and t ha-1), yield efficiency, biennial bearing index and fruit weight were studied in five plum cultivars ('Cacanska Rana, 'Cacanska Lepotica', 'Cacanska Najbolja', 'Cacanska Rodna' and 'Stanley') grafted on myrobalan (Prunus cerasifera Ehrh.) seedlings. Trees were planted at a spacing of 4×2 m (1,250 trees ha-1). Five-year results showed that the final tree vigour, expressed as trunk cross-sectional area (TCSA), was the lowest in 'Cacanska Lepotica' (39.9 cm2) and the highest in 'Cacanska Rana' (75.0 cm2) and 'Cacanska Najbolja' (82.9 cm2). 'Cacanska Rodna' and 'Cacanska Najbolja' gave their first yields as early as the second year (1.08 and 1.47 kg tree-1, respectively), whereas the first significant yields in all cultivars were obtained in the third year. Cumulative yield was the lowest in 'Cacanska Rana' (30.75 kg tree-1 and 38.44 t ha-1), somewhat higher in 'Cacanska Najbolja', 'Cacanska Lepotica' and 'Stanley' (43.86, 60.37 and 73.40 t ha-1, respectively), and the highest in 'Cacanska Rodna' (66.36 kg tree-1 and 82.95 t ha-1). However, 'Cacanska Rodna' had the highest biennial bearing index (0.61), whereas the other cultivars exhibited a moderate or poor biennial bearing habit during the experimental years. The lowest biennial bearing index was recorded in 'Cacanska Lepotica' (0.13). Yield efficiency was the lowest in 'Cacanska Rana' (0.12 kg cm-2) and highest in 'Cacanska Rodna' (0.41 kg cm-2). The average fruit weight was in agreement with cultivar-specific traits, and ranged from 27.4 g in 4Cacanska Rodna' to 51.8 g in 'Cacanska Rana'.