Abstract
Though there has been reported by some workers that draining a paddy field generally tended to suppress tillering of the plants on it, the present authors have found many exceptions in the matter by their five years' experiments. The influence differed according to the growth stage. When draining was started at the growth revival stage of the plant after transplanting, it affected the tillers to decrease in number. But when started at the critical stage where the last fructiferous tillers develop, of when started at the floral initiation stage, draining was found more favorable for increase of tillers rather than continuous submergence. Draining decreased the ammonium content in the soil at every stage. It made the soil temperature low in cooler weathers, but high in hotter one. It depressed the nitrogen absorption at the earlier stage, but promoted it at the later stage. Greater importance should be assigned to the soil temperature and the nitrogen absorption than the water content and the ammonium amount in the soil as the factors affecting tillering.
