Studies on the Development and Distribution of Roots and its Soil Conservation Faculty in Tea Plants : IV. Influences of subsoil improvement and irrigation on the development of tea roots

Abstract

To hasten the growth of tea plant in the replanting field, the effectiveness of layer-mixing plowing before planting and the effectiveness of irrigation and compost application after planting was investigated at the diluvial soil of Makinohara hill, Shizuoka prefecture in l969-1974. The growth of young plant was hastened by the irrigation and supply of compost in the soil. But the soil improvement by the layer-mixing plowing was not so effective during 5-6 years after planting. The reasons for the above facts may be as follows: (1) Although physical property of soil was improved by the layer-lnixing plowing, there still remained an impermeable layer consisted of coagulated gravels in a deeper zone. It was found later that root development was further improved when this impermeable layer was broken. (2) However, the growth of aerial part was not affected by the layer-lnixing plowing except on the breakdown of impermeable layer. This is becausc the chcmical fertility of soil was decreased by its being mixed with deep soillayer. Therefore, the soil amendment materials must be applied in combination with the improvement of physical property of soil by the breakdown of impermeable layer. Also the root growth by the irrigation was more affected when this impermeable layer wvas broken.