Effects of timing of nitrogen topdressing on morphological traits in different rice [Oryza sativa] varieties
2007
Fukushima, A.(National Agricultural Research Center for Kyushu Okinawa Region, Koshi, Kumamoto (Japan))
The effects of timing of nitrogen topdressing on morphological traits were investigated in three rice varieties: Hinohikari, Takanari and Akenohoshi. Rice plants in the field were topdressed 39 days before heading (very early), 29 days before heading (early),19 days before heading (standard), and 8 days before heading (late). The number of differentiated spikelets per panicle was the largest for early topdressing, and the number of degenerated spikelets per panicle was the smallest for standard topdressing. As a result, the number of spikelets per panicle was the largest for early and standard topdressing. Leaf blades and sheaths were longer in the leaf position where the leaf was rapidly elongating at the time of topdressing. However the length of internode was not clearly affected by the topdressing timing. The leaf area index was increased by very early and early topdressing, but the top dry weight was not clearly affected by the timing of topdressing. The number of shoots per area was increased by very early topdressing, but the number of panicles per area was not different among very early, early and standard topdressing. The number of spikelets per area was the largest for early and standard topdressing. The responses to topdressing for the number of differentiated spikelets per panicle, the length of leaf blade, and the leaf area index were the largest in Takanari. These results suggest that it is important to distinguish varietal differences when measuring the morphological response to nitrogen topdressing.
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