Abstract
An experiment was carried out during rabi 2017-18 and 2018-19 at Regional Research and Technology Transfer Station, Chiplima, Sambalpur, Odisha of Odisha University of Agriculture and Technology to study the influence of temperature stress at different sowing dates to on yield attributing characters, yield and economics of rice (Oryza sativa L.) cultivars. Rice sown on 10th December utilizedmore thermal and heat units as compared to 30th December and 10th January sown crop. The differential yield response of cultivars to various sowing dates was found to be due to their differential tolerance against high temperature at reproductive growth phase. On an average, 15.7 to 25% reduction in rice yield was obtained in case of sowing dates where temperature stress coincided with reproductive growth phase. The crop sown on 10th December took maximum growing degree days units to attain differentphenological stages till physiological maturity. Number of grains panicle-1 and rice yield increased with delay in sowing time up to 30th December, whereas there was a decrease in duration and tillers m-2. December 30 sown rice registered the highest grain yield (7.3 t ha-1), grain yield heat use efficiency (3.2 kg ha-1 0C day-1) and dry matter heat use efficiency (6.8 kg ha-1 0C day-1). Maximum number of grains panicle-1, grain yield, grain yield heat use efficiency, dry matter heat use efficiency and benefit cost ratio of rice cultivar MTU 1156 sown on 30th December seems to be associated with non-coincidence of their reproductive growth period with heat stress and seedling growth periods with cold stress. Cultivar MTU 1001 showed moderate tolerance to temperature stress and thus recorded lower heat susceptibility index (0.65) and higher yield stability ratio (84.5).
Highlights
Atmospheric temperature plays a significant role in deciding grain yield in rice
All P2O5 was applied as basal and N was applied in 3 splits, i.e. 50% as basal, 25% at 20 days after transplanting (DAT) and 25% at 40 DAT, while K2O was applied in two splits, i.e. 50% as basal and 50% at 40 DAT
Average mean temperature received by the rice cultivars from sowing to harvesting under different transplanting dates have been depicted in figure 1
Summary
Atmospheric temperature plays a significant role in deciding grain yield in rice. The crop duration under different dates of sowing of rice are greatly influenced by temperature and may be estimated by accumulated heat unit (Gauri et al, 2005). Neither too early nor too late sowing proved to give better yield response by offering prolonged growing period while eliminating chances of heat stress during reproductive growth phase of rice (Baloch et al 2006, Safdar et al 2008, Laborte et al 2012). The reproductive process occurs within 1 hour after dehiscence of anthers. It is followed by shedding of pollens, germination of pollen grains on stigma and elongation of pollen tubes.
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