Abstract
The causes and prevention of the leaf dying symptom of the melon was investigated which had broken out in the calcareous soils of Kikaijima Island, Kagoshima Prefecture. The results obtained are summarized as follows : 1) The competitive inhibition of magnesium absorption by the excess absorption of calcium, which was characteristic in the calcareous soils, was considered to be the cause of the leaf dying symptom. 2) The leaf dying symptom was prevented through the foliar spraying of magnesium solution at the beginning of the outbreak. 3) The leaf dying symptom was also prevented through the application of MgSO_4 which decreased the Ca/Mg ratio of the soils to 6. 4) The excess application of potassium increased the leaf dying symptom. We consider that this was because potassium in the soil enhanced the competitive inhibition of magnesium absorption by calcium.
