クリ黒根立枯病の発生と土壌環境

Abstract

A survey was taken on the occurrence of black root rot of chestnut, the amount of roots and the soil properties in two red-yellow soils and in Andosol. Furthermore, an experiment was done to compare the differences in growth of chestnut seedlings among these soil species and a granite weathered sandy soil. 1. The occurrence of the black root rot was more extensive in the chestnut groves on the brown forest soil that had been improved topographically and where red-yellow soil constituted the topsoil. In contrast, the occurrence was significantly less in groves on Andosol. 2. In Andosol, the amounts of fine root below 1 mm in diameter were more numerous than in the red-yellow soil. 3. In the three phase distribution, the red-yellow soil had a larger solid phase volume and a smaller gaseous phase volume than the Andosol. Soil water tension throughout the year fluctuated more in the red-yellow soil than it did in Andosol. 4. Potted chestnut seedlings had more roots less than 5 mm diameter and more mycorrhiza-infected roots in the Andosol compared to those grown on red-yellow soil. These findings suggest that in the Andosol, the occurrence of black root rot is less frequent because the chestnut trees undergo less water stress. This reduced water stress in the Andosol is attributed to the presence of more fine roots, minimizing soil moisture fluctuation throughout the year compared to the red-yellow soil and granitic, sandy soils.