Pg. 16-26 Use of rest-breaking agents for the timely stimulation of budbreak to improve flowering and production in litchi

Stimulation of growth by rest-breaking agents in the beginning of winter, when conditions are favorable for flower initiation, can improve flowering and production in litchi. Rest-breaking agents were applied during mid-April (1.5 & 3.0% KNO3, 0.5% LB urea, 0.05% Ethapon® and 0.05% Ethapon® in combination with 3.0% KNO3), end-April (1.5 and 3.0% KNO3, 0.5% LB urea, 0.4% Kelpak® and girdling) and mid-May (3.0% KNO3) in the Malelane area. Ethapon® treatments were applied on the mid-April flush. All rest-breaking agents gave a more uniform flushing when compared to the
control. Flowering was not significantly affected, but the time of full female bloom was earlier for the Ethapon® treatments, 0.5% LB urea (mid-April) and 1.5% KNO3 (end-April). Fruit set was not significantly affected by any of the treatments. The 0.5% LB urea treatment (end-April) gave significantly higher fruit drop while no significant effect was observed on fruit drop for the other treatments. Fruit size was significantly improved by the 0.4% Kelpak® treatment, probably as a result of the phytohormones in the product. There was no significant improvement in production, although 3.0% KNO3 (mid-April), girdling (end-April) and 3.0% KNO3 (mid-May) improved production by 1.0, 0.9 and 1.8 ton/ha respectively. In the Nelspruit area, branch treatments were done with concentration ranges of KNO3 (1, 2, 3 and 4%) and LB urea (0.25, 0.5 and 0.75%) in order to find optimum concentrations. No significant trends were observed for flowering, fruit retention and fruit size. Three percent KNO3 applied at the end of April gave a significant improvement in fruit set. Three percent KNO3 applied mid-April or mid-May (at the time of flower initiation), as well as girdling at the end of April proved, therefore, to be the most promising treatments overall.

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