Pruning Strategies for Young ‘Nadorcott’ Mandarin Trees Planted in High Density Orchards in South Africa

Abstract

The present study evaluated the effect of pruning according to different tree forms on yield, fruit size, and leaf starch reserves of young 'Nadorcott' mandarin trees planted at high density. Trees were selectively pruned by hand either according to form (pyramid or open center) by removing either lateral or central branches, or were left unpruned until trees touched each other in the row with minimal pruning thereafter (control). Form pruning, in particular the pyramid form, resulted in higher amount of biomass removal compared with the control treatment, affecting canopy volume and trunk cross-sectional area (TCSA). This led to a yield reduction in the first year, but steady yield increases in subsequent years. Fruit size was significantly larger in pyramid and open-center-shaped trees compared with the control treatment, but this difference declined as trees got older. Production efficiency (yield/canopy volume) of the pyramid form was significantly higher after the second year of pruning compared with the other treatments. Pruning did not influence leaf starch content, but indirectly affected crop load and subsequently the following year's crop size. Judicial removal of lateral branches, e.g. in pyramid-shaped trees, appeared to be the most beneficial tree form for 'Nadorcott' mandarin as it is closest to its natural growth habit and promotes sustainable yields with good marketable fruit size.

Citrus Pruning in the Mediterranean Climate: A Review

“…The central leader training system gives the tree a pyramidal shape (Figure 15) [107]. This training system can only be chosen if the grower intends to establish a high-density orchard (Figure 15a) [107][108][109], and is best suited for upright-crown-shape cultivars (Table 1) such as lemons (1 m × 3 m) [107] and 'Afourer' mandarin (1.5 m × 5 m) [108].…”

Pruning Boosts Growth, Yield, and Fruit Quality of Old Valencia Orange Trees: A Field Study

“…For leaf area (cm 2 ), we collected a sample of 20 mature leaves at the end of the growth season (the fifth distal leaf on the shoot) from five leaves from the four origin directions of the orange tree. We also recorded the length and width measurements, and then calculated the leaf area (cm 2 ) using the following equation [15]: leaf area (cm 2 ) = 0.49 (length × width) + 19.09. To estimate the volume of the tree canopy (m 3 ), we measured the height and diameter of the Valencia orange tree using a steel measuring tape for each experimental tree.…”

“…It is attempted after top working, frame working, and pruning [13]. In any case, top working and pruning may be used to prevent citrus orchard decline if the extent of the decline, age of the tree, soil and climatic conditions, and other factors are favorable [14,15].…”

The Perfect Match: Adjusting High Tree Density to Rootstock Vigor for Improving Cropping and Land Use Efficiency of Sweet Orange

“…Apart from productivity, functionality has also become a desirable attribute for production systems of fruit crops [23][24][25][26]. Nevertheless, there are few studies on the ease of fruit harvesting due to the tree size [78][79][80].…”

“…Regardless of its potential to boost early productivity, high-tree-density plantings require greater investment and may lead to the reduction of yield due to excessive tree crowding and difficulties in operations [22]. To address such limitations, the tree size control has been evaluated in high-density citrus orchards, including the use of pruning [23], training systems [24], irrigation [25], and dwarfing rootstocks [26]. This last method is considered the most suitable to ensure that trees will be permanently trained to the allocated space, besides facilitating several practices including harvesting, scouting, and spraying [27].…”