Vol. 12 No. 2
Thermal indices and growth attributes of rice hybrids under varied planting time and spacing during boro season
Author(s): B. SAHA, M. GHOSH, D. MAZUMDAR AND S. A. KHAN
Abstract: The phenophase-wise thermal indices and growthrnattributes of two rice hybrids under varied planting environment and spacingrnwere studied at Instructional Farm (22o93’N, 88o53 ’E andrn9.75 m.s.l), Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, WestrnBengal, India during boro season of 2012-2013. Mean summed growing degree daysrn(GDD) from sowing to emergence, fourth leaf emergence, active tillering,rnpanicle initiation, 50% flowering, milk, dough and maturity stages were 38.2 ,rn227.1, 514.6, 838.6, 1423.0, 1624.3, 1820.1, 2030.2ºC day, respectively. Ricernhybrids planted on 29 January accumulated lower total GDD (2003.7ºC day),rnheliothermal units (16966.1ºC day hour) and vigour index (1063.1) compared torntwo later plantings (12 and 27 February). Close spacing (15 × 15 cm) resultedrnin greater leaf area index (2.22 and 4.72) and dry matter production (109.4 andrn462.9 g m-2) at 28 and 70rndays after transplanting (DAT) than wider spacing (20 × 15 cm). Both hybrids (rnKRH 2 and Kumud) had more upright leaves (low light extinction coefficient, k =rn0.28 – 0.29) at mid growth phase. There was negative correlations between GDDrnand HTU during reproductive stage (panicle initiation to 50% flowering) andrngrain yield, but GDD during 50 per cent flowering to milk showed positive (P<0.05)rneffect on economic yield of hybrid rice.
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