Changes of sink/source ratio by application rate of basal nitrogen and planting density and its significance for yielding ability in rice plant
1989
Yamamoto, Y. (Kochi Univ., Nankoku (Japan). Faculty of Agriculture) | Yoshida, T. | Enomoto, T. | Yoshikawa, G.
This study was undertaken to clarify the effects of nitrogen application rate in basal to top dressing at panicle formation stage and planting density on the relative development of sink (number of spikelets per m2) and source (Leaf Area Index [LAI] at heading time), that is, sink/source ratio. We also discussed the relationship between the sink/source ratio and the dry matter production or yielding ability for the establishment of a stable high-yielding cultural method, using young seedlings, in the southern district of Japan. The results are summarized as follows: 1) Sink/source ratio changed mainly depending on the amount of source, not on that of sink. As LAI was increased in proportion to planting density, the higher the planting density was, the lower was the sink/source ratio. On the other hand, the effect of nitrogen application rate in basal dressing on the sink/source ratio was less, and it was little changed among plots applied 20-100% nitrogen in basal dressing, except for the non-basal nitrogen application plot, in which sink/source ratio was increased because of less development of leaf area. 2) The effect of planting density on the yield was markedly greater than that of nitrogen application rate in basal dressing. With increasing planting density, the higher brown rice yield obtained was due to both superior percentage of ripened grain and 1,000 grain weight. 3) The sink/source ratio showed significant negative correlation with the top dry weight at heading time, but not any significant correlations with the amount of absorbed nitrogen until then or dry matter production during the grain-filling period
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