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Supervisors: 1. Prof. Dr. TRAN HOP
2. Dr. DUONG CONG KIEN
ABSTRACT
Dendrobium Sonia (D. Sonia) is the cut-flower orchid commonly grown in Ho Chi Minh city. The study aims at to improve the fertilizer management to enhance Dendrobium Sonia obtaining more economic value. In particular, how (i) to determine the effect of P, Ca and boron B on growth and flowering; (ii) to determine the effect of three plant growth regulators as cytokinin (Cyt), ABA and nitrophenol (Ntp); (iii) to evaluate the interaction among three elements of NTDD (P, Ca and B) and three plant growth regulators (Cyt, ABA, Ntp); (iv) to evaluate the effect of basic fertilizer treatment on yield and quality flowers of D.Sonia at productive stage.
D. Sonia (D. ceasar x D. tomie) at 9 and 12-month old from Thailand was treated in the medium of 50% coconut husk + 50% charcoal. Nine-month old seedlinds obtained 18-20cm tall, pseudorange diameter of 0.9-1.1 cm, 2-3 pseudobulbs/pot. Twelve-month-old seedlings obtained the length of 24 - 26 cm, pseudorange diameter 1.0-1.1 cm, 3-4 pseudobulbs/pot. All selected orchids were required uniform phenotype, in particular number on pseudobulbs, length, diameter and number of leaves. Pot size: 18 x 9 x 12 cm.
At the appropriate concentration level, the 9 month-old Sonia orchid produced more new pseudobuls as compared to the 12 month-old ones (2.0 - 2.7 folds)
The independent treatments and combination treatments (3 nutrients) exhibited their flower longlife in terms of 12 month-old Sonia better 9 month-old Sonia as 1.7 to 2.0 folds.
The treatment of P1000ppm+ Ca90ppm+ B40ppm well adapted to 9-month-old Sonia, otherwise, P1250ppm+ Ca70ppm +B40ppm for 12-month-old Sonia orchid offered negative effect.
Cyt, Ntp and ABA did not well affect to the growth and the flowering of 9 month-old Sonia in term of simultaneous application of three nutrients. However, but 12-month-old Sonia responsed significantly to the three plant growth regulators at flowering with the treatment of Cyt = 20 and 25 ppm, Ntp = 15 and 19 ppm, ABA = 3 and 5 ppm.
Combination of three nutrients (P, Ca, B) and three plant growth regulators (Cyt, ABA, Ntp) to flowering of both 9-month-old Sonia and 12 month-old one indicated that 12-month Sonia expressed better flower number 9-month Sonia from 1.7 to 2.0 folds, especially inflorescence number per plant obtained 2.3 as compared to 1.3; pseudobulb length of 50.5 cm as compared to 44.0 cm; flower number / inflorescence of 11.8 as compared to 6.2
Two optimal combinations for the 12-month Sonia were recommended as Opt1: P1250ppm + Ca70ppm + B40ppm + Cyt20ppm + Ntp15ppm + AbA3ppm and Opt2 : P1250ppm + Ca70ppm + B50ppm + Cyt20ppm + Ntp15ppm + ABA3ppm.
The basic fertilizer and optimal combinations (3 nutrients and 3 plant growth regulators) for 12-month Sonia were reported as new pseudobuls (2.2 nos), pseudobul length (1.18 cm), number of leaves / pseudobulb (7.3), inflorescence / plant (2.2 nos), inflorescence length (51.7 cm) and flower number / inflorescence (12.3 nos).
Commercially, the requirement of orchid production and the optimal treatment were recommended as (P1250 + Ca70 + B40) + (Cyt20 + Ntp15 + AbA3 + Ph-8) + ( 50% VC + 50% HC)
Combination of the DD + DH (1250 + 70 + 40) + (20 + 15 + 3) + (50% VC + 50% HC) with 8 spraying times per crop obtained better yield with flowering percentage of 87% per plant, inflorescence no. / plant / year of 4.9 nos; total number of inflorescence / ha / year of 628,435 nos, inflorescence length of 48.0 - 52.0 cm, flower number / inflorescence of 10.8 nos; total number of flowers / ha / year of 6,808,345 nos.
Particularly, the net profit increased 80% as compared to the current practices by farmers. The protocol how to apply suitable fertilizer management and plant growth regulator for Dendrobium Sonia at the productive stage has been submitted.
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