Abstract
As a soil retention force of tea roots seemed to be influenced by the variety, planting density and soil moisture, the resisting power to stump-pulling was measured using several varieties. The soil retention force of tea roots varied with varieties. Kanayamidori and Okumidori, in which roots were well developed under the ground, had strong soil retention force, but Yabukita and Yamakai, which had comparatively less density of roots and many slender roots, had weak soil retention force. Also, the soil retention power of tea roots varied with the planting density and soil moisture. The denser the plant spacing, the weaker the soil retention force of a plant, however, the stronger was that per unit area. And the soil retention force under much soil moisture was weaker than that under less soil moisture condition.
