Growth and yield of lowland rice in response to shade and drainage.
1989
Chaturvedi G.S. | Ingram K.T.
Rice (Oryza sativa L.) is most susceptible to yield reduction by shade and water deficit during panicle emergence and flowering. Effects of shade before and after flowering in the growth and development of lowland rice and their interactions with drainage effects during panicle emergence and flowering were studied in a field experiment during the 1987 wet season with three rice cultivars - IR46, IR64, and Mahsuri. Postflowering shade (50% reduction of incident radiation) 5 to 20 days after panicle emergence (DAPE) had a more adverse effect on yield than preflowering shade from 10 to 25 days after panicle initiation (DAPI). Preflowering shade resulted in reduced leaf area, tiller number and spikelet/panicle, whereas post-flowering shade reduced filled spikelet, fraction and grain weight. Crop growth rate (CGR) was reduced more by preflowering than by postflowering shade, but CGRs of both shade treatments were less than those of unshaded controls. Drainage from 20 DAPI to 10 DAPE, which resulted in maximum soil moisture tension of 30 K Pa, reduced leaf area and all yield components. When shade and drainage stresses were combined, the effects were mostly additive. As compared to IR64 and Mahsuri, IR46 had the highest CGR and dry weight of leaf blade and sheath, and the least reduction in yield. It was concluded of the cultivars tested, IR46 had the greatest shade and drainage tolerance during panicle emergence and flowering owing to its ability to form and set spikelets using accumulated assimilates.
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