Mitsuo Kido

Relation between Aeration of the Soil and Growth of Rice Plant with Special Reference to the Morphology and Respiration of Root.

At a glance at a map of the paddy fields in Hokuriku District, we may easily be acquainted with that about sixty three per cent of the total area is occupied by ill-drained fields. Il-drained paddy fields are unfavorable not only for culture of rotation crops of paddy rice but also for growth of rice plant when compared with well-drained one. The fact may be partially attributed to root decay and reduction of absorption of nutrients such as silica and potassium. In order to ascertain the fundamental differences between ill-drained paddy field and well-drained one, that is, to make clear the differences in the plant growth caused by the difference in aeration of the soil, several experiments were carried out, in which growth of seedlings, morphology and respiration of root, and content of silica in leaves were observed. Results are summarized as follows: (1). In the plant grown under well aerated soil, compared with that grown which worse aeration, no remarkable differences in height of seedlings and length and width of leaf blades were observed, but the vigorousness of development in stem and root was distinguished. (2). Good aeration of the soil promoted elongation of root, resultting in the deep development of root system and numerousness of roots. (3). With good aeration of the soil, the formation of lysigenous aerenchyma and deterioration in root were suppressed and number of silicified cells leaves increased very remakably presumably owing to high oxidation-reduction potential.

The effect of Baido-pushing-up the soil aside the hill-upon the growth of rice plant and its rotation crops in ill-drained paddy fields

1. In order to know the effect of Baido, a practice to push up the soil aside the hil1, upon the growth of rice plant and of following crops in rotation on ill-drained paddy fields, investigations were carried out in the field of the Hokuriku Agricultural Experiment Station. 2. The best time for Baido practice was 33 days prior to heading ; i.e. the time when fruitful tillerings had developed, and when it was delayed, the crop yield decreased owing to the unrecoverable injuries of roots. 3. Increase of yield caused by the Baido method may be analyzed as follows : (1) Retardation of the development of unfertile tillerings. (2) Delayed formation of lysigenous aerenchyma, indicating checked decay of root because of high oxidation-reduction potential of soil. (3) Lessening the damages by sesame spot and stem rot.(4) Deep development of root system and increased number of roots. (5) The healthy growth and development caused by larger diurnal fluctuation of soil temperature. 4. The favorable effects of Baido not only upon the rice plant, but also on the rotation crop ascribable to the good aeration of soil were observed.