Time of pruning affects fruit abscission, stem carbohydrates and yield of macadamia

Abstract

Macadamia (Macadamia integrifolia Maiden and Betche, M. tetraphylla Johnson and hybrids) orchards in Australia are typically hedged around anthesis (September). Such hedging reduces yields, largely through competition for carbohydrates between early fruit set and the post-pruning vegetative flush, but also through a reduction in photosynthetic capacity caused by the loss of canopy. We examined whether hedging at other times might mitigate yield losses. Hedging time was found to affect yields across four cultivars: ‘A4’, ‘A38’, ‘344’ and ‘816’. Yield losses were lower for trees hedged in November–December than for trees hedged in September. Yields for trees hedged in June were higher than for trees hedged in September in one experiment, but were similar in a second experiment. Yield losses for September and October hedging were similar. Hedging time changed the pattern of fluctuations in stem water-soluble carbohydrates (WSC). WSC declined shortly after hedging in September, October or November, and the declines preceded increases in fruit abscission relative to unpruned control trees. The increase in fruit abscission was less pronounced for the trees hedged in November, consistent with the idea that fruit become less sensitive to carbon limitation as they mature.

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

“…The reduction in yield and ultimately income due to hedging might be minimized by hedging at a time that the post-hedging shoot growth did not overlap with early fruit development and reduce fruit set (McFadyen et al, 2012).…”

“…We had anticipated that the timing of topping, in late November at around 10 weeks post anthesis and at the end of the normal premature fruit drop period (Sakai and Nagao, 1984;Trueman and Turnbull, 1994), would minimize any effect of pruning on fruit set. In macadamia, light tip-pruning of trees in late November resulted in less fruit drop and higher yield than pruning trees in September or October around flowering and early fruit development (McFadyen et al, 2012). However, in citrus, severe pruning that was applied after the premature fruit drop period still reduced fruit number (Eissenstat and Duncan, 1992).…”

“…Side-hedging and topping contained tree size but not without a significant reduction in yield, especially in the case of topping. The effect of light regular side-hedging on yield may be minimized by timing hedging after the premature fruit drop period (McFadyen et al, 2012). However, it is not clear if the effect of more severe pruning as occurs with topping can be similarly mitigated.…”

Initial Effects of Fertilization and Canopy Management on Flowering and Seed and Oil Yields of Jatropha curcas L. in Malawi

“…Pruning alters carbohydrate allocation from flowers and fruits to healing the wounds, response to pest, and disease and vegetative growth of new flush shoots [30,[38][39][40][41][42]. In Zambia, high J. curcas branch mortality and low resistance to pest and diseases were observed after pruning (own observation).…”

Conserving Open Natural Pollination Safeguards Jatropha Oil Yield and Oil Quality

“…The 2-year-old plantation in Zambia was pruned (about 1/3 of the total vegetative part was removed). Pruning could have physiological consequences since the plant needs more energy to healing the wound and replace the lost photosynthetic leaves [58,59] than flowering, fruiting and fat synthesizing and accumulating in the seed organ. In both sites, we had good rainfall about 802 mm and temperature (26°C mean maximum and 14°C mean minimum), which is on the range of the species's growth requirement for rainfall and temperature, and they may not be a limiting factor for low oil content and quality in the sites.…”