Browsing by Author "Dedekind, Ruben Egmund"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- ItemInvestigating the vegetative development and yield of pecan(Stellenbosch : Stellenbosch University, 2020-04) Dedekind, Ruben Egmund; Lotze, Elmi; Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture.ENGLISH ABSTRACT: Like other deciduous trees grown in regions that experience warm winters and low winter chilling, pecans suffer from low and sporadic bud break. This often has negative implications for vegetative growth and development of the trees, especially in younger orchards that are still filling space. Furthermore, the yield will often be reduced as a result of reduced vegetative development as well as a lack of synchronisation in the flower development. Application of hydrogen cyanamide (HC) formulated as Dormex® was evaluated on two pecan cultivars, ‘Wichita’ and ‘Navaho’, grown in the Prieska region, Northern Cape, South Africa. Three different concentrations were evaluated on two application dates. Trees were assessed for time of bud break, final percentage of total bud break, shoot growth and yield. Additionally, the effect of HC on the synchronisation of the flowering periods of ‘Wichita’ as the main cultivar and ‘Navaho’ as the cross pollinator, was assessed. During 2018, after a relatively cold winter, Dormex® had a relatively small effect on the bud break parameters of ‘Wichita’ trees. On ‘Navaho’ trees, all treatments were effective at increasing the percentage bud break. During 2019, a warmer winter was experienced. On ‘Wichita’, an early application four weeks before expected bud break (4WBBB) was more effective at advancing bud break than a later treatment, two weeks before expected bud break (2WBBB). Dormex® at 4% resulted in a significantly higher initial bud break percentage than the control on both cultivars and Dormex® at 4% and 2%, resulted in a significant increase in the final percentage bud break during the warmer year. These results indicate the total bud break (vegetative and reproductive buds) and do not indicate improved vegetative development or improved flowering per se. No increase was seen in vegetative bud break during the 2019 season on either cultivar and this should be evaluated further. Dormex® at 4% 4WBBB resulted in a significantly higher yield on ‘Wichita’ compared to the control during the first season and this needs to be followed up during 2020. No increase in yield was seen on ‘Navaho’. The best result for improving the synchronisation of the flowering periods was achieved by treating ‘Wichita’ with 4% Dormex® 4WBBB to significantly advance bud break, while leaving ‘Navaho’ trees untreated. No signs of phytotoxicity on leaves or shoots were observed for any of the treatments. In conclusion, the effect of HC on improving the vegetative development of these cultivars could not be established, as no distinction was made between vegetative and reproductive buds during bud break and more research is required. HC applications did however influenced time and percentage bud break. It is possible that the effect could be extended towards yield through better synchronisation of the flowering periods, but this effect can only be quantified during 2020 and thus could not be included in this thesis. The effect of notching shortly before bud break was investigated on young, nonbearing ‘Wichita’ pecans grown in the Villiersdorp region, Western Cape, South Africa. The effect on bud break, shoot number, shoot length and branch angle was evaluated. On two-year-old wood, notching was unable to increase bud break or shoot number and was influenced to a certain extent by the size of the bud. No increases were seen in shoot length on two-year-old wood. On one-year-old wood, notching significantly increased the number of. In conclusion, notching can increase lateral vegetative development of young trees if carried out on younger wood and could be used as a valuable tool for improving vegetative development and ensuring more successful orchard establishment.