Sulfur dioxide gas injury to fruit trees. II.

Actual conditions of suffered citrus trees and survey of their nutritional status

Abstract

In 1961 and 1962, Satsuma orange trees grown in Shimotsu district of Wakayama prefecture suffered greatly from smoke pollution. This paper refers to its actual conditions and the result of leaf analysis of the affected trees.
1. Most of suffered leaves presented the symptom of SO₂ injury showing the smoky spots, and some of them expressed the symptom of sulfuric acid mist injury having the small poxlike spots. Besides, some of leaves shed down rapidly without showing any of diseased spots.
2. Soil acidity in the affected orchard was much greater at the 10cm-deep than at 30cm-deep layer. However, no significant correlation was found between the soil pH and the SO₂ concentration in atmosphere, its coefficient (r) being -0.2.
3. S content of leaves in the affected orchard was generally high, and it was highly correlated with SO₂ concentration in atmosphere. The correlation coefficients between them in July and September of 1963, and January of 1964 were +0.85, +0.78 and +0.79, respectively. S content of leaves increased with their age from July of 1963 to January of 1964. Its increasing rate was greatest when the SO₂ gas flowed in the orchard.
4. High negative correlation existed between S and Ca contents of leaves, having the coefficient(r) of -0.67. K and Mn contents of leaves increased as S content of leaves increased, though no significant correlation was found. N, P and Mg contents of leaves had no connection with S content of leaves.
Thus, the composition of nutritional elements in suffered Satsuma orange trees seems to be much affected directly or indirectly by the SO₂ concentration in atmosphere.