Effect of Depth of Transplantation on the Growth and Yield of the Rice Plant

[摘要] Some field experiments were carried out to know the effect of depth of transplantation on the growth and yield of the rice plant aiming mainly to obtain informations for experimental procedure. (1) Deep transplantation caused retardation of the maximum number of tillers stage and slight retardation of the heading and the ripening stage. (2) Deep transplantation caused the plant to decrease the height of plant and the number of tillers comparing with the case of shallow transplantation in the early stage of growth, but no difference was found between deep and shallow transplantation in the height of plant, stem length and the number of leaves on the main stem at the ripening stage. As the tillering period is limited, deeply transplanted plots, which showed a growth depression at the early stage, could not catch up with the shallowly transplanted plots in the number of tillers, resulting in small number of heads, in spite of high ratios of the effective tillers being obtainted. (3) A negative correlation was found between the number of heads and the number of spikelets per head, but the former was positively correlated with the number of spikelets per unit area. The percentage of ripened grains and the weight of 1, 000 grains decreased as the number of heads increased. No significant difference in yield was found between deep and shallow transplantation, though a slightly better yield was recognized in the latter case. (4) Therefore, the primary ill-effect of deep transplantation seemed to be the retardation of rooting caused by the abnormal elongation of tillering node, which induced the decrease of the number of tillers and consequently that of heads. The effect on the number of spikelets per head, fertility and the weight of 1, 000 grains was considered to be secondary, because clear compensatory reactions were observed between yield-components. (5) This tendency which exists between plots can also be recognized between the individual plants transplanted as a group in the field, namely, a shallowly transplanted plant always brought about a vigorous growth, high yield and a large individual variation. (6) Even when little difference in yield was found between different depths of transplanting, the growth of plant was considerably affected, which meant that the effect could hardly be neglected from the view point of growth process. (7) An optimum depth of transplantation seems to be 3 cm, though it depends on the conditions of cultivation, and ill-effects were found in the cases transplanted above 5 cm depth.

[学科分类] 农业科学（综合）