Sayan Sdoodee and Rawee Chiarawipa

pp. 719 - 730

Abstract

Fruit splitting is a serious problem of Shogun mandarin in southern Thailand. To alleviate this
impact, the applications of calcium and boron by spraying were investigated. An experiment was established
in a farmer orchard (at Amphur Sadao, Songkhla province) where four-year plants were grown at 6 m x 6 m
spacing. The experiment was arranged as a completely randomized design, and 16 trees were used. There
were 4 treatments (1. control or water spray, 2. 1% CaCl₂
 spray or C treatment, 3. 0.8% boric acid spray or
B treatment and 4. 1% CaCl₂
+ 0.8% boric acid spray or C+B treatment) with 4 replicates. The application
was started at 4 months after fruit-setting, the sprays were done at 1 month intervals. It was found that the
occurrence of fruit-splitting started at 3 months after fruit-setting, and there were 4 causes of fruit-splitting: 1. scab (28.33%), 2. sun scald (11.11%), 3. sun burn (7.78%) and 4. no primary peel damage (52.78%). Various
patterns of fruit splitting were found: vertical, horizontal, oblique and informal shape. The treatments of
calcium and boron sprays did not affect on fruit growth or fruit size compared with the control, but they
significantly enhanced fruit firmness, total soluble solid (TSS) and total acidity (TA). The treatments of C, B,
and C + B can reduce the percentages of fruit splitting to 5.56, 8.89 and 6.67%, respectively, and they were
significantly different from that of the control (52.22%). It is suggested that calcium and boron sprays can
alleviate fruit splitting in Shogun mandarin, and fruit quality is also enhanced.