Quantifying the potential of almond production in the Western Cape for future extension and high-density plantings in suitable climatic regions

Thesis (MScAgric)--Stellenbosch University, 2022.

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.

AFRIKAANSE OPSOMMING: Die gewildheid van die amandel (Prunus amygdalus Batsch) het toegeneem onder Suid-Afrikaanse produsente weens die behoefte aan beter alternatiewe gewasse in die Weskaap. Produsente soek ook meer doeltreffende en volhoubare produksiemetodes wat insette sal verminder om wêreldwyd mededingend te bly. Hoë- digtheid aanplantings blyk om meer winsgewend te wees in kommersiële gewasse soos perske en nektarien as tradisionele lae-digtheid aanplantings, maar gepaste blaardakbestuur en manipulasies is nodig om die doeltreffendheid van hierdie stelsels te handhaaf. Die doel van hierdie studie was om verskillende spasiëring en opleistelsels vir twee kommersiële kultivars te assesseer om toekomstige opbrengs potensiaal te maksimeer. Die Soleta kultivar se blaardakontwikkeling en prestasie in twee nuut gevestigde super-hoë-dighteid (2049 bome.ha -1) opleistelsels in die Robertson area is geëvalueer. Die studie het gefokus op die verhouding tussen ligonderskepping en potensiële opbrengsdoeltreffendheid, aangesien die boord gedurende die eerste twee seisoene in 'n vegetatiewe fase was. Die oopkelk (OK) stelsel het sterker groeipatrone getoon, wat gelei het tot 'n betekenisvolle hoër stamomtrek (in al drie seisoene), lootgroei en blaardakvolume na somersnoei (2020/21) en ligonderskepping tydens volblom (2020/21;2021/22). Die OK het 'n betekenisvolle hoër stamomtrek area gehad, wat gelei het tot die betekenisvolle hoër opbrengsdoeltreffendheid in die twee- as (TA) stelsel in 2020/21. Die OK het 'n betekenisvolle hoër in-dop- en neut gewig, - lengte en -breedte gehad. Aanvanklike resultate het aangedui dat beide stelsels geskik is vir 'Soleta' in super-hoë-dighteid, maar die TA stelsel het beter gevaar as die OK stelsel met betrekking tot opbrengsdoeltreffendheid in die eerste kommersiële oes (drie jaar na vestiging). Die effek van twee alternatiwe onderstamme, 'Viking' en 'Flordaguard', op die vegetatiewe ontwikkeling van 'Nonpareil', is in die Durbanville area geëvalueer. Die onderstam het nie die stamomtrek of die gemiddelde jaarlikse lootgroei gedurende die twee opeenvolgende seisoene beïnvloed nie. Die onderstam het wel blaardakvolume na die voltooiing van lootgroei beïnvloed, asook die ligonderskepping, na blaarval. 'Nonpareil' bome op 'Flordaguard' het 'n betekenisvolle hoër blaardakvolume en ligonderskepping as bome op 'Viking' gehad, wat aangedui het dat 'Flordaguard' tot ‘n meer groeikragtige 'Nonpareil' bostam gelei het as 'Viking'. Amandelverbouing teen hoër digthede is 'n relatief nuwe konsep teenoor die historiese, tradisionele stelsels wat tans gebruik word. ’n Finansiële vergelyking is getref tussen die prestasie van die Soleta (meer kompak, self-bestuiwende) en Nonpareil (kragtige, kruis-bestuiwende) kultivars in die Durbanville-, Robertson- en Montagu-streke, geplant in verskillende boordstelsels, met verskillende plantafstande en opleistelsels. Vir elke stelsel is die netto huidige waarde (NHW) en aangepaste interne opbrengskoers (AIOK) bereken. Die NHW teen 'n verdiskonteringskoers van 5% en 10% het aangedui dat die lae-digtheid stelsel vir beide kultivars verkies word. ’n Sensitiwiteits analise is uitgevoer vir die jaar wat voldrag behaal word, asook vir die boord se lewensverwagting. Met die uitsondering van die AIOK, wat met 1% toegeneem het vir 'n twee-jaar afname in die lewensverwagting van lae-digtheid boordstelsels, het beide faktore 'n negatiewe impak op die NHW en 'n negatiewe of geen impak op die AIOK gehad.

Masters