This study was carried out to investigate the toxic effects of boron on the 10-year-old jujuba trees(Zizyphus jujuba Miller) on which applied approximate 21.6 ㎏/10a, 7 times as much as normal levels. Some of the results obtained are summarized as follows:
1. The content of boron in the jujube orchard decreased from 4.59 ppm on June 3 to 0.57 ppm on Sept. 24.
2. The leaves of jujube trees applied with excessive boron turned yellow from the end of May with marginal necrosis and inward curlings. At the same time, the lower leaves of branchlet and flower clusters were severely fallen. In addition, much fruit drop was observed in the early of July.
3. On June 3, the content of boron in the leaves on the jujube trees applied with excessive boron was 279 ppm, remarkably high compared with the normal, 41ppm. In addition, absorption of P and K was inhibited in jujube trees showing B-toxicity symptom.
4. Poor blanchlet growth and fruit russeting were observed with jujube trees applied with excessive boron from early stage of fruit development.
5. Soluble solids content of fruits with excessive boron application was much lower(26.2%) compared to the normal(38.5%). Moreover, the fruit weight of the trees with excess boron application was much lower than that of the normal.
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