Production Trends in Mature Macadamia Orchards and the Effects of Selective Limb Removal, Side-hedging, and Topping on Yield, Nut Characteristics, Tree Size, and Economics

Abstract

<jats:p>Yields of macadamia (<jats:italic>Macadamia integrifolia</jats:italic>, <jats:italic>M. tetraphylla</jats:italic>, and hybrids) orchards tend to increase with increasing tree size up to ≈94% light interception. Beyond this, there is some indication that crowding leads to yield decline, but the evidence is limited to one site. Increasing tree size and orchard crowding also present numerous management problems, including soil erosion, harvest delays, and increased pest and disease pressure. The aim of this study was to better characterize long-term yield trends in mature orchards and to assess the effects of manual and mechanical pruning strategies on yield, nut characteristics, tree size, and economics. We monitored yield at four sites in mature ‘344’ and ‘246’ orchards for up to seven years and confirmed a decline in yield with crowding for three of the sites. There was a small increase in yield over time at the fourth site, which may reflect the lower initial level of crowding and shorter monitoring period compared with the other sites, and highlights the need for long-term records to establish yield trends. Pruning to remove several large limbs from ‘246’ trees to improve light penetration into the canopy increased yield relative to control trees but the effect was short-lived and not cost-effective. Removal of a codominant leader from ‘344’ trees reduced yield by 21%. Annual side-hedging of ‘246’ trees reduced yield by 12% and mechanical topping of ‘344’ trees caused a substantial reduction in yield of up to 50%. Removal of limbs in the upper canopy to reduce the height of ‘344’ trees had less effect on yield than topping but re-pruning was not practical because of the extensive regrowth around the pruning cuts. Tree size control is necessary for efficient orchard management, but in this study, pruning strategies that controlled tree size also reduced yield. Research into the physiological response to pruning in macadamia is required to improve outcomes.</jats:p>

Phenotypic Association of Multi-scale Architectural Traits with Canopy Volume and Yield: Moving Toward High-density Systems for Macadamia

“…Hedging may negatively affect yield by removing fruiting age wood Wilkie et al, 2009), stimulating competitive vegetative growth (Wilkie et al, 2010), and lowering the photosynthetic potential of newly exposed shade leaves (Huett, 2004). Selective limb removal has been shown to increase and to have no effect on or to decrease yield compared with unpruned trees (McFadyen et al, 2013;Olesen et al, 2011). The reduction in yield is related to the amount of biomass removed, which is probably related, at least partly, to reduced light interception .…”

“…Controlled vigor, early flowering, high partitioning of resources to productive processes, and high yield per hectare are key attributes of intensive temperate orchards that will benefit future macadamia orchards. However, crowding, shading, and the refinement of advanced training and pruning techniques remain obstacles to subtropical crops such as macadamia and avocado (McFadyen et al, 2004(McFadyen et al, , 2013Menzel and Le Lagadec, 2014). The discovery and incorporation of less vigorous scion cultivars and dwarfing rootstocks may be the most effective means of controlling vigor and increasing canopy efficiency for macadamia; however, there is currently limited research regarding such cultivars and little understanding of canopy architecture specific to macadamia (Huett, 2004;Nagao et al, 1992).…”

Effects of Early Tree Training on Macadamia Production

“…Early tree training from planting slowed the expansion of the canopies (Fig. 1) and this too might have had a detrimental effect on yields, given that macadamia production tends to increase with increasing orchard light interception (McFadyen et al, 2004b(McFadyen et al, , 2013.…”

“…The cropping pattern of the trees in our study was typical of that of commercial orchards, with no yield in the first few years after planting, then an exponential increase in yield in the first few years of production. However, macadamia does have large yearto-year variations in yield (McFadyen et al, 2004b(McFadyen et al, , 2013 and it is not clear the extent to which these have distorted the developmental response.…”