EFFECT OF ELEVATED CO2 AND TEMPERATURE ON GROWTH AND YIELD OF WINTER RICE UNDER JORHAT CONDITION
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Date
2019-07
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AAU, Jorhat
Abstract
A pot experiment was conducted during kharif, 2018 to assess the effect of elevated CO2 and temperature under different transplanting dates on growth and yield of rice variety Ranjit. The treatment composed of three CO2-temperature levels [T0: ambient temperature & ambient CO2, T1: elevated temperature (ambient +1°C) & elevated CO2 (ambient+25% of ambient) and T2: elevated temperature (ambient +2°C) & elevated CO2 (ambient + 50% of ambient)] and three dates of transplanting (D1: 25th June, D2: 10th July and D3: 25th July). The experiment was conducted in three CO2 Temperature Gradient Tunnels (CTGTs) following factorial CRD with 4 replications. Occurrence of different phenological stages like tiller initiation, panicle initiation and flowering was earlier under elevated CO2-Temperature condition which significantly differed with the ambient condition. On the other hand, days to tillering increased whereas days to panicle initiation, flowering and physiological maturity reduced with delay in transplanting. The crop duration was reduced by about 15 days and 8 days under T2 and T1 respectively compared to T0 and by about 10 days and 5 days in D3 and D2 respectively compared to D1. Reduction in the duration of vegetative phase was found to be more distinct than the reproductive and ripening phases. Accumulated agro-climatic indices viz., AMaxT, AMinT, AMeanT and AGDD showed a gradual decline with delay in date of transplanting from 25th June onwards during vegetative, reproductive and maturity stages irrespective of CO2-Temperature treatments. Similarly, accumulated agro-climatic indices decreased under elevated CO2-Temperature during vegetative stage but increased during reproductive and ripening phases of the crop. Plant height and tiller number was recorded highest under T2 followed by T1 compared to T0, which decreased with delay in transplanting. Both plant height and number of tillers differed significantly in CO2-temperature treatment as well as dates of transplanting. Number of panicles hill-1, panicle length, number of filled grains panicle-1 and 1000-grain weight were significantly influenced by elevated CO2-temperature levels and date of transplanting. Number of panicles was greater but filled grains panicle-1 slightly reduced under T2. With respect to dates of transplanting, D2 recorded higher number of panicles hill-1 (17.9) and higher filled grains panicle-1 (156.6). Higher grain yield (55.9g hill-1) attributed to higher number of panicles hill-1 and filled grains panicle-1 was observed under T2 which was at par with T1 and it was statistically significant over ambient. Grain yield significantly reduced (40.6g hill-1) when transplanting was delayed after 10th July. Similarly, straw yield and above ground biomass at harvest were significantly increased with CO2-temperature elevation but reduced with delay in transplanting. Though the interaction effect of CO2-temperature and dates of transplanting on rice yield was not statistically significant, the results revealed that the growth and yield of rice variety Ranjit was found to be better under elevated CO2-temperature levels when transplanted on 10th July.