抄録
The test material was ripening plants. The plants were grown in 150 paddy fields at Aomori, Akita, Yamagata, Fukushima, Chiba, Saitama, Nagano, Fukui, Hiroshima, Kouchi and Saga prefectures in Japan (Table 1). Superficial roots were collected by means of the soil-core sampling method. Core, consisting of a cylindrical tube with an internal diameter 5 cm and 5 cm height, was pressed vertically into the soil up to 5 cm in ten places in the middle of intrarow spacing (Fig. 1). The degree of superficial root formation is shown by the average weight of roots involved in the soil core. Value of yield of hulled rice was calculated in terms of field per 10 are. It has been found that superficial root weight is correlated with the field of hulled rice (Fig. 3). In case of the fields which produced yields between 180 kg and 600 kg hulled rice, superficial root weight and yield of hulled rice showed a considerable value of correlation coefficient (r=+0.831). In case of the fields which produced yields between 601 kg and 801 kg of hulled rice, superficial root weight and yield of hulled rice showed relatively lower correlation coefficient (r=+0.313) as shown in Fig. 4. From these results, it has been assumed that superficial root formation contributed to rise of the yield of hulled rice. Also it can be reported that, the importance of root system is not only due to its superficial root but also contributed to the root grown into both the plow layer and subsoil.
