Effect of near canopy thermal changes on growth, yield and grain sterility of three ultra-short age rice varieties under aerobic and flooded conditions

Canopy temperature (CT) represents the temperature experienced by the uppermost portion of the vegetative canopy of a crop. CT may better explain the high temperature-induced grain sterility and yield losses than air temperature does. However, less scientific attention was paid on CT related investigations on rice under Sri Lankan context. Therefore, Sri Lankan rice varieties were evaluated at the Rice Research and Development Institute, Bathalagoda under two soil moisture conditions to study the canopy thermal dynamics and its impact on growth, grain sterility and yield. This Experiment was arranged in a two-factor factorial Completely Randomized Design with eight replicates. Factor one was soil moisture condition (aerobic and flooded) and factor two was rice variety (Bg 250, Bg 252 and Ld 253). CT was continuously monitored at 10 minutes intervals. Growth and yield parameters were recorded once a week. Number of tillers was negatively correlated with maximum CT while plant height was positively correlated with minimum CT in both conditions. CT at spikelet opening had a negative impact on pollen fertility and positive impact on grain sterility irrespective of moisture condition. Under flooded condition, grain yield was negatively correlated with maximum CT at 13:00 h. Moreover, growth and yield performances were superior under flooded conditions compared to aerobic conditions. Interactive effect of soil moisture × variety was significant for 1000-grain weight and % pollen fertility where the 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 growth and yield performances of rice under varying soil moisture conditions. Field investigations are suggested to confirm the results.