EVALUATION OF 'LAPINS' SWEET CHERRY ON DWARFING ROOTSTOCKS IN HIGH DENSITY PLANTINGS, WITH OR WITHOUT PLASTIC COVERS

Five ‘Lapins’ sweet cherry planting systems, with and without plastic covers, were compared from 1993 to 1999: slender spindle (3.5 x 1.5 m), Le Page hedge (2.5 x 1.5 m), super spindle (2.5 x 1.0 m), vertical cordon (2.0 x 0.5 m), and cordon in Güttinger V-hedge (2.5 x 0.4 m); tree number/ha varied from 1,900 to 10,000. Trees in the slender spindle and Le Page systems were grown on three rootstocks, Inmil (GM9), Damil (GM61/1), and Edabriz (Tabel^®); the other three systems used trees on Inmil and Edabriz. Edabriz was the most productive rootstock. Cumulative production per tree over the first 5 cropping years, for slender spindle and Le Page, was 35.4 kg for Edabriz, 15.0 kg for Inmil, and 13.8 for Damil. Fruit weights on Edabriz, Inmil and Damil averaged 9.8, 9.7, and 10.0 g, respectively. Cumulative yields on Edabriz, Inmil and Damil were 30.4, 16.1, and 10.6 kg/tree without plastic covers and 40.4, 13.9, and 17.0 kg/tree under covers, respectively. Plastic covers appeared to increase production but the differences were not statistically significant. Covering resulted in a significantly higher (0.8 g) fruit weight averaged for all tree shapes. Without covers, 32.9% of the fruits cracked vs. 24.3% under covers.
The higher the planting density, the higher the cumulative yield per ha. Slender spindles (1,900 trees/ha) on Edabriz produced 68.3 mt/ha, while cordons (10,000 trees/ha) on Edabriz yielded 116.2 mt/ha. Fruit weight was highest on the slender spindles (10.1 g) and smallest (9.4 g) on the cordons. The higher the planting density and the more vigorous the rootstock, the higher the light interception. Edabriz cordons intercepted 75% of incoming light vs. 17% with slender spindles on Inmil. The plastic covers reduced incoming light by 14%, which was the probable cause of the observed decreased sugar content in covered fruits. Perceived flavor did not vary between fruits from slender spindles and vertical cordon trees on Edabriz, either with or without plastic covers. The flavor of fruits from both tree shapes without covers was similar, but fruits from covered slender spindles were judged to be of better flavor than those from covered cordons. The V-hedge system (`Lapins’ on Edabriz) had the highest Annuity Net Present Value (ANPV). However, due to high investment costs for systems with 10,000 trees/ha and the risks for lower average prices/kg due to lower fruit quality, the super spindle system was the most economical.