MSc

The present investigation on “Simulation of environmental and varietal effects
in rice using CERES model” were carried out in Department of Agricultural
Meteorology, College of Horticulture, Vellanikkara during 2012-13 to determine the
crop weather relationship, to calibrate the genetic coefficient and simulation of
phenology, growth and yield of Jyothi and Kanchana varieties of rice. The experiment
was laid out in split plot design with four replications at Agricultural Research Station,
Mannuthy during the Kharif season of 2013. Five dates of planting was assigned as a
main plot treatment viz., 5th June, 20th June, 5th July, 20th July and 5th August with two
varieties (Jyothi and Kanchana) as sub plot treatment.
The different growth and yield characters like plant height, leaf area index, dry
matter accumulation,1000 grain weight, grain yield, straw yield, number of panicles,
spikelets, filled grains and duration of different growth phases were recorded along with
monitoring the incidence of various pest and diseases. The daily weather parameters
like maximum and minimum temperatures, forenoon and afternoon relative humidity,
forenoon and afternoon vapour pressure deficits, bright sunshine hours, evaporation,
wind speed, rainfall and rainy days were determined.
The minimum temperature, afternoon and forenoon relative humidity, rainfall,
rainy days, bright sunshine hours and evaporation were found to be higher in early
planting dates compared to late plantings. Plant height, leaf area index, dry matter
accumulation, yield and yield attributes were highly variable among the different
planting dates. Yield and yield attributes were influenced by various weather parameters
experienced by the crop during different dates of planting. Days taken to complete
maturity were reduced with each successive delay in planting dates in both the varieties.
Genotypic variations are found between the varieties but days taken for each
phenophases were found to be similar. June 5th and July 20th planting recorded the
highest yield in Jyothi whereas June 20th and July 5th planting gave highest yield in
Kanchana. Jyothi was found to be superior to Kanchana during the crop season.
To determine the critical weather elements affecting the crop growth, correlation
analysis was done and it was observed that crop duration would decrease with increase
in temperature and bright sunshine hours whereas, the forenoon and afternoon relative
humidity, rainfall and rainy days showed a positive influence on crop duration. Multiple
linear regression models were fitted, to predict the grain yield based on weather
variables.
The crop genetic coefficients that influence the occurrence of developmental
stages in the CERES-rice models were derived, to achieve the best possible agreement
between the simulated and observed values. Calibration was done with the independent
data sets of two rice varieties viz. Jyothi and Kanchana for different genetic coefficients,
which characterize the performance of the crop.
The performance of the CERES-rice simulation model was tested and evaluated
using the calibrated genetic coefficients for both the varieties with their respective
planting dates. The results of simulation studies in respect of phenophases and yield of
rice were compared with the observed values from the field experiment. Root Mean
Square Error (RMSE) and D- stat (index of agreement) were used to evaluate the
model performance and found that predicted yield of both rice varieties Jyothi and
Kanchana under different planting dates were reasonably close to the observed values.