Steyn, JacobusJoubert, ElsjeMushezha, Rolivhuwa2026-01-162026-01-162025-09-05Mushezha, R. 2025. The effect of product formulation on the uptake efficacy of micronutrient elements applied as foliar sprays and how micronutrients affected fruit set and yield of Macadamia trees. . .https://univendspace.univen.ac.za/handle/11602/3084M.Sc (Ecology)Department of Geography and Environmental SciencesFoliar fertilization has lately been advocated by some advisors as being a more efficient method of fertilization than soil applications and has been promoted as a viable economic way to supplement the plants’ nutrients (Girma et al., 2007). Through foliar fertilizations, nutrients can be delivered directly to the target organs during critical periods of rapid uptake creating little opportunity for its runoff and waste. The factors affecting the uptake and translocation of foliar applied nutrients by mist blower applicators which produce atmospheric aerosols are however, poorly understood. Many trace elements are also notorious for poor uptake and translocation in plants and many gaps in knowledge in this regard, exist (Niu et al., 2021; Hu et al., 2023). An experiment was conducted to investigate the impact of different formulations of zinc (zinc oxide, zinc nitrate, and zinc chelate) and iron (iron sulphate and iron chelate) on the uptake efficiency of these micronutrient elements when applied as foliar sprays to macadamia trees. Additionally, the study aimed to assess how these micronutrients, along with various other elements (including magnesium, manganese, boron, copper, calcium), as well as two products containing multiple nutrient elements (namely Kelpak (cold pressed seaweed), and Budding Mix (a blend of essential trace elements for budding and fruit set in trees), influenced fruit set? fruit drop? and final yield in macadamia trees. Field trials were conducted in macadamia orchards where trial plots contained 200 macadamia trees each. The trees were of the same cultivar i.e. Beaumont (or ‘695’) and age of 23 years old. A total number of 9 treatments were applied where each trial plot was sprayed three times over a 3-month period to coincide with 3 important phenological stages of the macadamia trees i.e., flowering, fruit set and fruit drop. Each treatment contained a trace element or combinations of trace elements and other nutrients and these were applied as foliar sprays on the leaves of the trees. A control plot received no treatment. Nutrient uptake of the different zinc and iron formulations in the macadamia leaves were analysed and compared and fruit set, fruit drop and final yield were measured for all treatments and compared. Results showed that zinc nitrate was not significantly better taken up by the macadamia leaves compared to the zinc oxide and zinc chelate formulations but showed significantly higher zinc contents than the control. The other two formulations did not show results that significantly differed from the control. Concerning the iron formulations, iron sulphate was not taken up significantly higher than the Fe chelate formulation, but the leaves contained significantly more iron than the control although the Fe chelate formulation did not significantly differ from the control. The second phase of the study produced mixed outcomes. Among all the foliar element spray treatments, Zn nitrate demonstrated the best performance in terms of fruit set, albeit with the highest incidence of fruit drop. Conversely, Zn oxide applications led to the highest yield among all treatments in the final yield results. The evaluation of final yield was particularly crucial, representing the most significant aspect of the study from a commercial agricultural standpoint. While final yields did not show significant differences in many cases among treatments, a gross income analysis revealed slight increases in yield (nuts harvested per hectare), resulting in substantial income boosts. Some treatments resulted in more than R30 000 income per hectare than the control. This finding is noteworthy as South African macadamia nuts are exported, generating foreign currency, and positioning them as a high-value crop. Although the results from this study did not reveal significant and clear outcomes in terms of foliar applications of microelements for the commercial macadamia farming industry, it made two important contributions; firstly, that foliar applications of microelements are indeed a viable way of supplementing micro element deficiencies and secondly, this study demonstrated some knowledge gaps which have also been also been cited by other researches like Hu et al., (2023) and the need for more research in the field of applying micronutrients with the aid of foliar applications for plant nutrition.1 online resource (xii, 105 leaves): color illustrations, color mapsenUniversity of VendaUCTDDissertationMushezha R. The effect of product formulation on the uptake efficacy of micronutrient elements applied as foliar sprays and how micronutrients affected fruit set and yield of Macadamia trees. []. , 2025 [cited yyyy month dd]. Available from:Mushezha, R. (2025). <i>The effect of product formulation on the uptake efficacy of micronutrient elements applied as foliar sprays and how micronutrients affected fruit set and yield of Macadamia trees</i>. (). . Retrieved fromMushezha, Rolivhuwa. <i>"The effect of product formulation on the uptake efficacy of micronutrient elements applied as foliar sprays and how micronutrients affected fruit set and yield of Macadamia trees."</i> ., , 2025.TY - Dissertation AU - Mushezha, Rolivhuwa AB - Foliar fertilization has lately been advocated by some advisors as being a more efficient method of fertilization than soil applications and has been promoted as a viable economic way to supplement the plants’ nutrients (Girma et al., 2007). Through foliar fertilizations, nutrients can be delivered directly to the target organs during critical periods of rapid uptake creating little opportunity for its runoff and waste. The factors affecting the uptake and translocation of foliar applied nutrients by mist blower applicators which produce atmospheric aerosols are however, poorly understood. Many trace elements are also notorious for poor uptake and translocation in plants and many gaps in knowledge in this regard, exist (Niu et al., 2021; Hu et al., 2023). An experiment was conducted to investigate the impact of different formulations of zinc (zinc oxide, zinc nitrate, and zinc chelate) and iron (iron sulphate and iron chelate) on the uptake efficiency of these micronutrient elements when applied as foliar sprays to macadamia trees. Additionally, the study aimed to assess how these micronutrients, along with various other elements (including magnesium, manganese, boron, copper, calcium), as well as two products containing multiple nutrient elements (namely Kelpak (cold pressed seaweed), and Budding Mix (a blend of essential trace elements for budding and fruit set in trees), influenced fruit set? fruit drop? and final yield in macadamia trees. Field trials were conducted in macadamia orchards where trial plots contained 200 macadamia trees each. The trees were of the same cultivar i.e. Beaumont (or ‘695’) and age of 23 years old. A total number of 9 treatments were applied where each trial plot was sprayed three times over a 3-month period to coincide with 3 important phenological stages of the macadamia trees i.e., flowering, fruit set and fruit drop. Each treatment contained a trace element or combinations of trace elements and other nutrients and these were applied as foliar sprays on the leaves of the trees. A control plot received no treatment. Nutrient uptake of the different zinc and iron formulations in the macadamia leaves were analysed and compared and fruit set, fruit drop and final yield were measured for all treatments and compared. Results showed that zinc nitrate was not significantly better taken up by the macadamia leaves compared to the zinc oxide and zinc chelate formulations but showed significantly higher zinc contents than the control. The other two formulations did not show results that significantly differed from the control. Concerning the iron formulations, iron sulphate was not taken up significantly higher than the Fe chelate formulation, but the leaves contained significantly more iron than the control although the Fe chelate formulation did not significantly differ from the control. The second phase of the study produced mixed outcomes. Among all the foliar element spray treatments, Zn nitrate demonstrated the best performance in terms of fruit set, albeit with the highest incidence of fruit drop. Conversely, Zn oxide applications led to the highest yield among all treatments in the final yield results. The evaluation of final yield was particularly crucial, representing the most significant aspect of the study from a commercial agricultural standpoint. While final yields did not show significant differences in many cases among treatments, a gross income analysis revealed slight increases in yield (nuts harvested per hectare), resulting in substantial income boosts. Some treatments resulted in more than R30 000 income per hectare than the control. This finding is noteworthy as South African macadamia nuts are exported, generating foreign currency, and positioning them as a high-value crop. Although the results from this study did not reveal significant and clear outcomes in terms of foliar applications of microelements for the commercial macadamia farming industry, it made two important contributions; firstly, that foliar applications of microelements are indeed a viable way of supplementing micro element deficiencies and secondly, this study demonstrated some knowledge gaps which have also been also been cited by other researches like Hu et al., (2023) and the need for more research in the field of applying micronutrients with the aid of foliar applications for plant nutrition. DA - 2025-09-05 DB - ResearchSpace DP - Univen LK - https://univendspace.univen.ac.za PY - 2025 T1 - The effect of product formulation on the uptake efficacy of micronutrient elements applied as foliar sprays and how micronutrients affected fruit set and yield of Macadamia trees TI - The effect of product formulation on the uptake efficacy of micronutrient elements applied as foliar sprays and how micronutrients affected fruit set and yield of Macadamia trees UR - ER -