抄録
Root system formation in rice plants was studied by means of an improved monolith method in relation to ill-drained and well-drained conditions in four paddy fields belonging to farmers in Miyagi and Yamagata, prefectures in Japan. It was found that root system formation is affected by the drainage levels of paddy fields. Rice plants grown in an ill-drained paddy field with no mottling in the plow layer, with no structure in the subsoil, and with low grain yields had root systems that consisted of a small number of roots growing in both the plow layer and the subsoil. Rice plants grown in a paddy field soon after drainage with mottling in the plow layer, with no structure in the subsoil, and with high grain yields had root systems that consisted of a large number of roots, most of which grew in the plow layer and a few of which grew in the subsoil. Rice plants grown in a well-drained paddy field with mottling in the plow layer, with blocky structure in the subsoil, and with higher grain yields had root systems that consisted of a large number of roots growing into both the plow layer and the subsoil.
