Use of biostimulants as an alternate approach to achieve plant performance and fruit quality

[摘要] ENGLISH ABSTRACT: Research in fruit crops using biostimulants as a strategy to improve tree performance by alleviating transplant shock and improving both yield and fruit quality under field conditions, is limited. The main aim of this study was thus to determine the efficacy of biostimulants to enhance plant performance and quality of fruit trees under South African conditions. The specific objectives were to determine: i) the effect of a combination of biostimulants on growth and fruit quality of bearing 'Rubystar' plum and 'Forelle' pear cultivars, ii) the efficacy of a combination of biostimulants to reduce transplant shock and promote establishment of non-bearing 'Packham's Triumph' and 'Celina' pear trees and iii), the efficacy of the biostimulant application to improve transplanting and establishment success of 'Nadorcott' mandarin trees in the Western Cape, South Africa.The first experiment was conducted on the commercial farms of 'Bourgogne' in Franschhoek and 'Avontuur' in Villiersdorp, Western Cape, whereas the second and third experiments were conducted at the Stellenbosch University Welgevallen Experimental Farm, Stellenbosch. The first two studies consisted of two treatments: the control (no application) and a soil-based biostimulant combination (Rizofos Fruit®, Tri-Cure SP®, Premax® and Technical®).In the Franschhoek and Villiersdorp experiments, no significant differences were found between treatments, for either the plums or pears, with respect to vegetative growth and fruit quality parameters during the first season of application. However, a biological trend where the biostimulant treatment enhanced stem diameter, shoot length and yield efficiency, even though statistically non-significant compared to the control treatment in 'Rubystar' plums, warrants further investigation.Similarly, the second experiment also did not realise significant differences between treatments with respect to vegetative growth for either 'Celina' or 'Packham's Triumph' trees during the first season. When considering physiology however, the biostimulant treatment recorded a significantly higher stomatal conductance for 'Packham's Triumph' and 'Celina' compared to that of the control treatment.In the third experiment, five biostimulant treatments: compost (control), Terramax®, Kelpak®, RootAktiv® and Super Wortel® were evaluated. The RootAktiv® treatment had a significantly higher shoot growth than the Terramax® and Kelpak® treatments but was similar to the control. The Kelpak® treatment had a significantly higher root length and compared to the RootAktiv® and Super Wortel® treatments but was similar to the control. The Terramax® and Kelpak® treatments had a high SWP than Super Wortel® and RootAktiv® in March, whereas in May, Terramax®, Kelpak® and RootAktiv® treatments had a significantly higher SWP than the control and Super Wortel® treatments. The Kelpak® treatment showed significantly higher stomatal conductance than the control and Super Wortel® treatments, for the second evaluation date. Thus, contrary to expectations, significant differences and promising trends were already obtained after one season with young, non-bearing 'Nadorcott' mandarin trees. In addition, results suggest that the time of application and target organ (root or leaf) will be an important factor determining the efficacy of the applications.From the study, it was concluded that certain biostimulants, under specific conditions, showed promising trends in enhancing performance of perennial crops under field conditions. The importance of selecting the correct product for a specific goal, based on mode of action, was emphasised. Similarly, the lack of significant differences between treatments despite evident trends confirmed the importance of the conduction of field experiments over at least two or more consecutive seasons before final conclusions are drawn.

[发布机构] Stellenbosch University