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In hydroponics, the nutrient solution is supplied considering the water and nutrient uptake characteristics of crops. However, as the ionic uptake characteristics are changed as a result of the weather conditions or the growth response of the crops, the root zone can not be maintained in optimal condition. In addition, the coir substrate has been used mainly for the tomato cultivation in place of the inorganic substrate, there are few studies on long-term cultivation using coir substrate. Therefore, this study was conducted to investigate the effect of EC level of irrigation solution on tomato growth and inorganic ions of root zone in soilless culture using coir. Coir substrate mixed with 5 : 5 chip and dust was used. EC level of irrigation solution was 1.0, 1.5, 2.0, and 3.0 dS•m -1 . At the initial stage, NO 3 -N, P, Ca and Mg in the drainage were lower than the irrigation level at 1.0 and 1.5 dS•m -1 . However, EC 2.0 dS•m -1 or higher, all the ions except P were highly concentrated in the drainage. The average fruit weight was not significantly different between 1.0 and 1.5 dS•m -1 until 3th cluster, but from the next cluster, the higher the EC level, the smaller the weight. The number of fruit and yield to 6th cluster was the highest at 1.5dS•m -1 . From the next cluster, The yield was decreased with the higher EC level. At the early stage of growth, BER occurred only in EC 3.0 dS•m -1 , but increased in all treatments with increasing irradiation. The incidence rate of EC 3.0 dS•m -1 was higher than that of the lower EC level treatment.

Also, t-cincreaseisdecreasein order In hydroponics, the accumulation of inorganic ions in the root zone are closely related to the irrigation volume. Therefore, the effects of irrigation volume on the growth and yield of tomatoes are very signigicant. This study was conducted to investigate the effect of irrigation volume on inorganic ions of root zone in hydroponic culture using coir substrate. The irrigation volume was adjusted to 4 levels depending on the integrated solar radiation for each growth period. The drainage ratio was calculated by daily amount of irrigation and drainage. The higher irrigation volume is, drainage ratio and water absorption tended to increase. But, the water absorption in the treatment of high irrigation volume was decreased in February and March compared to the treatment of medium high irrigation volume. By calculating monthly average irrigation volume and the drainage ratio, 120 to 140 J/cm 2 in January, 100 to 120 J/cm 2 in February, 80 to 100 J/cm 2 in March, 70 to 90 J/cm 2 in April and 60 to 75 J/cm 2 in May was detected as appropriate irrigation volume ranges which drainage ratio was 20-30%. The higher irrigation volume, the lower the concentration of ions decrease, which could prevent the accumulation of nutrients in the root zone. However, due to the characteristics of the coir substrate that absorbs ions, concentration of ions was significantly high when the drainage ratio was 20-30%. However, concentrations of P and K were sometimes lower in the drainage than that of irrigation water regardless of the treatment. Mg and S were the most highly accumulated ions even in the treatment of high irrigation volume. In low radiation season, there was no difference in the ion concentration in the drainage depending on the irrigation volume. In high radiation season, the lower irrigation volume, resulted to the higher ion concentration in the drainage. After March, it was difficult to prevent the increase of ions concetration in the drainage by only adjusting irrigation volume. Thus, it is necessary to decrease the EC of irrigation solution to prevent the accumulation of nutrients in the root zone.

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