Masters Degrees (Horticulture)

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Browsing Masters Degrees (Horticulture) by Subject "Almond -- Climatic factors"

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    Quantifying the potential of almond production in the Western Cape for future extension and high-density plantings in suitable climatic regions
    (Stellenbosch : Stellenbosch University, 2022-04) Du Toit, Nina; Lotze, Elmi; Hoffmann, Willem H.; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: Almond (Prunus amygdalus Batsch) has become popular as an alternative crop with South African growers as the need for marginal crops in the Western Cape increases. Growers are also seeking more efficient and sustainable production methods that will reduce inputs to remain globally competitive. High-density plantings proved to be more profitable in commercial crops like peach and nectarine than traditional low-density plantings, but proper canopy management and manipulations are required to maintain the efficiency of these systems. The aim of this study was to assess different spacing and training configurations with respect to maximizing future reproductive potential, for two commercial cultivars. The canopy development and performance of two newly established super- high-density (SHD) (2049 trees.ha -1) training systems in the Robertson region were evaluated for the Soleta cultivar on ‘Garnem’ rootstock. The study focused on the relationship between light interception (LI) and potential yield efficiency, as the orchard was in a vegetative phase during the first two seasons. The Open-Vase (OV) system showed more vigorous growth patterns than Bi-Axis (BA), resulting in a significantly higher stem circumference (in all three seasons), shoot growth and canopy volume (CV) after summer pruning (2020/21) and LI during full bloom (2020/21;2021/22). The OV had a significantly higher trunk cross-sectional area (TCSA), which translated into the significantly higher yield efficiency in the BA system, in 2020/21. The OV had a significantly higher in-shell and kernel weight, -length and -width. Initial results indicated that both systems are suitable for ‘Soleta’ at SHD, but the BA system outperformed the OV system with regard to yield efficiency at the first commercial harvest (three years after establishment). The effect of two alternative rootstocks, ‘Viking’ and ‘Flordaguard’, on the vegetative development of ‘Nonpareil’, was evaluated in the Durbanville region. Rootstock did not influence the stem circumference or the average annual shoot growth during the two consecutive seasons. However, rootstock affected CV, after shoot growth cessation, and LI, after leaf drop. ‘Nonpareil’ trees on ‘Flordaguard’ had a significantly higher CV and LI than trees on ‘Viking’, which indicated that ‘Flordaguard’ resulted in more vigorous growth of the ‘Nonpareil’ scion than ‘Viking’. Almond cultivation at higher densities is a relatively new concept than the historical, traditional systems currently under production. A financial comparison was conducted on the performance of the Soleta (more compact, self-fertilising) and Nonpareil (vigorous, self-infertile) cultivars in the Durbanville, Robertson and Montagu regions, planted in different orchard systems, with varying planting densities and training systems. For each system, the net present value (NPV) and modified internal rate of return (MIRR) were calculated. The NPV at a discount rate of 5% and 10% indicate that the low-density system is preferred for both cultivars. A sensitivity analysis was performed on the year that full production is achieved, as well as on the orchard's life expectancy. With the exception of the MIRR, which increased by 1% for a two-year decrease in the life expectancy of low-density orchard systems, both factors had a negative impact on the NPV and a negative or no impact on the MIRR.