Abstract:
Canopy Temperature (CT) represents the temperature experienced by the uppermost
portion of the crop canopy. CT may better explain the grain sterility associated with high
temperatures than the air temperature. Most of the CT related experiments were
conducted on wheat. Therefore, Sri Lankan rice varieties were evaluated at the Rice
Research and Development Institute, Bathalagoda under two soil moisture conditions to
realize the canopy thermal changes and its impact on growth, yield, and grain sterility.
This Experiment was arranged in a two-factor factorial in Completely Randomized
Design with eight replicates. Factor one was soil moisture conditions, aerobic, and
flooded. Factor two was rice varieties; Bg 250, Bg 252, and Ld 253. CT, growth, and
yield parameters were recorded. CT at 10:00 h had a positive impact (r=0.76) on grain
yield in flooded condition and CT at 9:00 h had a positive impact (r=0.77) on yield in
aerobic conditions. Grain sterility increased with increasing CT in both moisture
conditions. The number of tillers was negatively correlated with maximum CT, while
plant height was positively correlated with minimum CT in both conditions. CT at
spikelets opening had a negative impact (r=0.76, 0.80) on pollen fertility at heading and
positive impact (r=0.95, 0.85) on grain sterility in both conditions. Moreover, growth and
yield performances were superior under flooded conditions compared to aerobic
conditions. Interaction between soil moisture and variety was significant for thousandgrain weight and pollen fertility % where highest values were recorded by Bg 250 (29.33
g) and Bg 252 (96.4%) in flooded conditions, respectively. In conclusion, monitoring CT
dynamics can be considered as a useful tool to assess the growth and yield performances
of rice under varying environmental conditions.
Keywords: Rice (Oryza sativa), Canopy temperature, Aerobic & flooded conditions,
Grain sterility, Pollen fertility
