Abstract
1) Some preliminary experiments were conducted with the object of knowing the condition of high productivity of paddy field scattered in the plain of Nakatado-gun, Kagawa-prefecture. 2) It was observed that the development of rice plant roots was better in highly productive fields than that a degraded fields. Concerning the relation between the amount of nitrogen supplied and the development of rice plant roots, dressing with more nitrogen did not necessarily mean better root development in the case of a paddy field of the Hiroshima Agricultural Experimental Station where the soil degraded, but in the case of a paddy field of the Shikoku Agricultural Experiment Station, where dressing with more nitrogen annually resulted in considerable increase in yield, the development of rice plant roots was greater in proportion to the amout of nitrogen increased, which fact is, in authur's opinion, a peculiarity of highly productive paddy field. 3) As to the results of measurment of base exchange capacity of rice plant root; the base exchange capacity of rice plant root in each layer of soil columns of highly productive paddy fields proved greater than that of degraded paddy fields. Again in the case of a paddy field of the Hiroshima Agaicultural Experiment Station, the amount of the supplied nitrogen did not noticeably changed base exchange capacity of rice plant roots, but in the case of a paddy field of the Shikoku Agricultural Experiment Station, which have a peculiarity of of yielding better crops, base exchange capacity of rice plant roots evidently increased in propotion to the amount of nitrogen increased.
