Masters Degrees (Horticulture)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/558

Browse

Browsing Masters Degrees (Horticulture) by Author "Brown, Robert"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Effect of permanent shade netting on ‘Nadorcott’ mandarin tree phenology and productivity
    (Stellenbosch : Stellenbosch University, 2018-03) Brown, Robert; Cronje, P. J. R.; Stander, Ockert P. J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: Permanent shade netting in citrus (Citrus spp.) is implemented to protect high-value fruit and trees from damaging natural elements. However, the use of the technology accompanies inevitable changes in orchard microclimate that impacts on the physiology and phenology of a citrus tree. In this study a 20% white permanent shade netting treatment was evaluated for its effects on citrus tree phenology, its impact on the efficacy of chemical fruit thinning agents, and the long-term profitability of the technology in a young ‘Nadorcott’ mandarin (C. reticulata Blanco) orchard. Shade netting did not enhance the growth of individual vegetative shoots but did increase tree volume over time. In general, flowering was not affected by the shade net treatment, but during the second season, flowering intensity on summer vegetative shoots was higher in the shade net treatment. Fruit set, fruit yield and fruit internal quality were not affected by the shade net treatment, but fruit diameter was increased in the second season. Shade netting did not influence the ability of uniconazole soil-drench treatment to reduce vegetative growth. The shade net treatment did not influence the efficacy of synthetic auxin fruit thinning agents to thin fruit. The synthetic auxin fruit thinning treatments increased the concentration of selected mineral elements in fruit, and treatments resulted in a shift in fruit size distribution, with higher number of large, premium-sized fruit per tree. The effect on fruit size distribution was more pronounced in the shade net treatment. Apart from fruit size, a combination of shade netting and chemical fruit thinning treatments had no effects on other important fruit quality attributes. From the budget model generated in this study, it can be concluded that 20% white permanent shade netting resulted in increased orchard profitability, despite a high establishment cost and increase in production costs. It can therefore be concluded that under typical Mediterranean-type production conditions, 20% white permanent shade netting increased the productivity and profitability of a ‘Nadorcott’ mandarin orchard. The use of the technology can be recommended in areas that experience extensive yield losses due to climatic conditions and possibly also permit citrus production in non-traditional areas.