Journal of Applied Horticulture. 2000 publ 2001: 2(1): 1-5

Pruning strategies to alleviate overcrowding in higher density citrus orchards

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

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

In this study different pruning methods were applied to higher density orange (cv. Navel), grapefruit (cv. Star Ruby) and orange (cv. Valencia) orchards (in South Africa, in 1996-99), which had become overcrowded five to six years after planting. A progressive decline in yield and fruit size was experienced with these orchards. Response to the different pruning actions, as well as yield variation and fruit size was assessed over three successive seasons. Corrective (severe) pruning and hedging resulted in a significant reduction in yield in the 1st year after pruning, but with an increase in fruit size. However, yield and fruit size improved substantially in the 2nd and 3rd year after the severe pruning. Light hedging as a maintenance pruning action was effective in restricting tree size without adversely affecting yield. Alternate bearing was substantially reduced by annual pruning. By creating a slanted, 20 degrees angle canopy with mechanical hedging and selective pruning, a greater portion of fruit is borne within reach from the ground. The narrower tree tops also improve light penetration. Regrowth developed more evenly over the total leaf area at this slanted angle. Mechanical hedging alone proved to be unsuccessful, due to the development of a too dense outer-canopy. All pruning methods eventually resulted in an increased yield and improved fruit quality compared to the unpruned control. A combination of mechanical hedging (10 degrees to 20 degrees ) and selective pruning (2-3 times/year), is the recommended procedure for alleviating overcrowding in higher density orchards.