The Influence of Photo-thermal Quotient on the Growth and Yield of Summer Rice under Varying Dates of Transplanting and Irrigation Regimes in Lower Gangetic Plains of India

Aims: The selection of transplanting windows of summer rice based on temperature and solar radiation is an important task to keep the production potential of this crop under changing climate scenario especially with deficit irrigation management.

Methodology and Study Design: Two years field experiment (2014 and 2015) was conducted in the Lower Gangetic Plains of Eastern India where the popular rice cultivar Satabdi seedlings of 35 days old, were transplanted on three dates with 14 days interval (24th January, 7th February and 21st February) as the main plot treatment. Four irrigation regimes [continuous ponding (I1); intermittent ponding (I2) during 20 to 65 days after transplanting (DAT) (irrigation applied 3 days after disappearance of standing water); irrigation depth is 0.05 m; intermittent ponding (I3) during 20 to 65 DAT (irrigation applied 5 days after disappearance of standing water); irrigation depth is 0.05m, and shallow depth deficit irrigation (I4) during 20 to 65DAT; irrigation depth is 0.03m.] were chosen as the sub-plot treatment. The design of the experiment was strip-plot.

Conclusion: It was found that aboveground biomass and panicle weight showed a linear function of the cumulative photo-thermal quotient (PTQ). From the regression analysis, it was found that PTQ at panicle initiation (PI) stage significantly and positively affected the grain yield. The present experiment identified that the summer rice could be transplanted from last week of January to the first fortnight of February with the I2 irrigation management when the impact of PTQ on grain yield and biomass production was maximum. The mean grain yield was 6.51t ha-1 compared to the general practice though they are not significantly different and the mean biomass production was 41.63 g m-2. The maximum temperature of 34.4 – 37.0°C and a minimum temperature of 22.0 – 22.5°C with radiation energy of 16.37 – 23.97 MJm-2 at PI stage were found congenial for good yield in summer rice.