Effect of climate change on the performance of lowland rice (Oryza sativa L.) under N- levels through DSSAT CERES- rice model
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Date
2018
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College of Post Graduate Studies in Agricultural Sciences, CAU, Imphal
Abstract
A field experiment was carried out during the kharif season 2017 at the experimental farm of the College of Post Graduate Studies (CAU, Imphal). The experiment was conducted in Two Factorial Randomized Block Design with 4 replications for 3 rice cultivars (CAU R1, Shahsarang1, Lumpnah1) under different N levels (80, 100, 120 and140 kg ha-1). Agronomic data were recorded throughout the crop growth period. Daily weather data related to the minimum and maximum temperature, rainfall and solar radiation were collected from the nearest meteorological station at ICAR Research Complex for NEH Region, Umiam, Meghalaya. The study was undertaken to validate CERES-Rice model, to conduct model sensitivity analysis to nitrogen levels and to study the impact of climate change on the yield of rice.
The results showed that all the growth parameters viz., plant height, tillers hill-1, dry matter production, Leaf Area Index (LAI), growth indices like Crop Growth Rate (CGR), Relative Growth Rate (RGR) improved with succession of crop growth period i.e. 30-90 days after transplanting (DAT) as well as at harvest. Among cultivars, Shahsarang1 recorded significantly higher plant height, dry matter production, LAI, CGR, RGR, yield and yield attributes over Lumpnah1 and CAU-R1. Among different nitrogen levels, significantly higher magnitude of above parameters were found at 140 kg N ha-1 followed by 120, 100 and 80 kg N ha-1. Shahsarang1 was found to be the better performer interms of growth and yield over other two cultivars viz. Lumpnah1 and CAU-R1.
The CERES-Rice model has been validated against the observed data (days to physiological maturity, grain yield and tops weight) recorded during kharif season 2017 for which model was calibrated in an experiment in 2016. Simulated values for different cultivars under varied nitrogen levels were in close agreement with observed values.The validation result was further supported by the statistical results where the per cent difference between observed and simulated values for various growth and yield parameters were well within the acceptable range of ±15%, with R2 values above 0.9, low root mean square error (RMSE) and d-stat values greater than 0.5 except for maturitydays.
The validated CERES-Rice model was then run for local sensitivity analysis where the sensitivity with respect to levels of nitrogen was considered. The model was found to be behaving satisfactorily to nitrogen levels for CAU-R1 and Shahsarang1 but not for Lumpnah1 cultivar of rice. Further calibration of Lumpnah1 may be required with crop data of few more years.
At current CO2 conc. decrease in rainfall average to -19% and -50% increased the grain yield by 0.3-18.7% while increase in average rainfall to +19 and +50% reduced the grain yield by -6.2 to -12.6%. However, for all change in temperature (±10C, ±20C and±30 C), reduction in grain yield by -1.4 to -43.1% was recorded. At 450 ppm CO2 conc. Increase in grain yield by 1.3-10.6% was obtained for all rainfall regimes. Similarly, for all changes in temperature scenario grain yield was increased by 1.6-8.9% except for 120 and 80 kg N level where the grain yield was reduced by 0.2 and 1.6%. Similar result was recorded for change in rainfall and temperature where the grain yield increased by 3.2-14.9% and 2-13% respectively. As for the combination, highest increase and decrease in grain yield at 450 ppm was reported for +1oC and +50% and -2oC and +50% of average rainfall, respectively. At 500 ppm, highest increase and decrease in grain yield was reported for +1oC and -50% and -2oC and +50% of average rainfall, respectively. However, at -3oC reduction in temperature, no grain was produced for all the cases. It was due to the drop of minimum temperature to lower than 150C at reproduction stages of the crops.
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Keywords
Rice, Climate change