Microclimate of Tropical Paddy Rice as Influenced by Water Management

Abstract

The effects of water management on the microclimate of paddy rice under tropical field conditions have not been well documented. This study investigates changes in the microclimate of paddy rice and its influence on rice yield under different water management. Field experiments were conducted for two cropping seasons in Nueva Ecija, Philippines. The treatments were continuous flooding (CF), saturated soil condition (SSC), and safe alternate wetting and drying (AWD). Significant changes in the rice microclimate were observed during the dry season, wherein drying the field was possible. A general trend showed lower soil, meristem, and canopy temperatures in AWD and SSC than in CF. Consistently, significantly lower temperatures ranging from 22.64‒28.13 °C were observed during the reproductive stage and 23.03‒28.47 °C during the maturity stage under water-saving techniques compared to CF across both daytime and nighttime. In all growth stages, the canopy temperature was significantly lower in AWD by 0.36‒0.48 °C at nighttime compared to other treatments. However, there was a shift of higher canopy humidity (> 80) in AWD (albeit not significant with CF) in both daytime and nighttime. Seasonal variations of the canopy temperature and humidity at nighttime showed lower in the dry season than the wet season. Under normal conditions, differences in microclimate between CF and AWD did not significantly affect the grain yield despite the water savings of the latter by 78%. The findings of this study underscore AWD's role in lowering the microclimate of the rice plant when there are extreme heat episodes in a tropical environment.