Differential effects between interplant competition and physical stress in rice seedlings
1994
Torres, R.O. | Kropff, N.J. | Matthews, R.B. (International Rice Research Inst., Los Banos, Laguna 4030 (Philippines). Agronomy, Plant Physiology and Agroecology Div.)
An experiment was conducted in 1993 dry season to separate the effects of seedling competition in the nursery from transplanting shock on the rice crop. Ten, 20, 30, and 40-day old seedlings of IR72 and IR58109-113-3-3-2 were grown by staggered sowing in wet beds (WB) at 100 grams seeds/sq.m. and in wet beds in hills (HWB) at 20 cm x 20 cm spacing with five seeds/hill. Each seedling age had a corresponding direct sowing (DS) in hills with the same spacing and population as HWB. Competition effects and transplanting shock effects were expressed as the difference of WB from HWB and DS from HWB, respectively. Competition suppressed tillering and caused tiller degeneration in the seedbed, thus, reducing tillers by 55 to 64 percent at 30 DAS, and leaf area index by 25 to 40 percent and total dry weight by 14 to 27 percent starting at 20 DAS. Prolonged period in the seedbed aggravated these effects. Transplanting shock in 20-day old seedlings delayed flowering by 6 to 7 days. Competition delayed flowering of 30 to 40-day old seedlings by 4 to 10 days. Panicle yield declined by 0.95 t/ha due to transplanting shock and by 0.87 t/ha due to competition in the 20-day old IR71 seedlings. The overall effects of competition and transplanting shock were not apparent with the 10-day old seedlings but were prominent with older seedlings
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