Abstract
The experiments on the influence of periodical and continuous drainage, and periodical circulation of irrigation water on the growth of rice were made using artificial paddy soils, during 2 years 1956-57. The results obtained were as follows :-(1) The growth of leaves and stems showed no difference between periodical circulation drainage and control, but it was less in continuous drainage than in control. (2) Circulation of irrigation water and drainage magnified roots-crowd, especially, periodical circulation and drainage increased number, dry weight, depth and vitality of roots. (3) The yields in the drainage plot was decreasd partly by the loss of nutrients in the soil, but the yeild was increased in the periodical circulation by about 8 % than that of the control, accompanied with vigorous growth of roots. (4) Summarily, circulation of irrigation water is useful in oxygen supply to roots-crowd, increase of soil temperature preventing loss of various nutrients, exclude of injurious gases, economy of water and beneficial for rice plants growing in submerged paddy field, especially in leakage soils, and Akiochi soils.
