Journal of Applied Horticulture. 2002: 4(1): 17-20

Manipulation of citrus trees for new higher-density orchards

Joubert, F J; Plessis, M H du; Steenkamp, E D; Stassen, P J C

ARC-Institute for Tropical and Subtropical Crops, Private Bag X11208, Nelspruit, 1200, South Africa.

Results of a study on the response of Valencia orange, mandarin, lemon and grapefruit cultivar/rootstock combinations to training systems (central leader system for high-density planting and multiple leader system for low-density planting), pruning methods (trees cut back to 50 cm height after planting and trained with new growth; trees shaped after planting without cutting back; trees shaped after 1 year of growth), and planting densities (3.0x1.0, 4.0x1.25, 4.0x1.5, 5.0x2.0 and 5.0x3.0 m, corresponding to 2222, 2000, 1667, 1000 or 667 trees/ha) are presented. The experiment was conducted in Nelspruit (Valencia orange and lemon), Lydenburg (mandarin) and Malelane (grapefruit), South Africa during 1996 and 1997. Pruning back a newly established tree to 50 cm height after planting had negative effects on tree volume and development compared to the other pruning methods. Lemon trees were trained more successfully under the central leader system. Higher levels of manipulation and pruning were necessary when lemon trees were trained under the multiple leader system, since leaders of the same strength and development phase were difficult to find. On the other hand, Valencia orange trees were more easily trained under the multiple leader system. Trees of lemon and Valencia orange exhibited greater canopy growth at higher densities (3.0x1.0 and 4.0x1.5 m, respectively).