Climatic factors related to low rice (Oryza sativa L.) yield in the wet season under double cropping in the Mekong Delta, Vietnam

Abstract

This study aimed to determine the rice (Oryza sativa L.) yield under douhle cropping in the Mekong Delta, Vietnam, and idenlify which climatic lactors cause a reduced yield in the wet season (WS) compared with the dry season (DS). A series of field experiments was conducted in the field from 2014 to 2017, along with a supplementary pot experiment, by using the rice variety OM 6976. The yield was 38% lower in WS than in DS, mainly due to a decrease in the spikelet number per panicle and percentage of ripening. This yield reduction observed in WS was most closely related to lower radiation at 51-80 days after transplanting, and was also related to higher temperature. These results suggest that low radiation and high temperature during the reproductive to grain-filling stages were mainly responsible for causing a lowyield in WS. In addition. a need to further consider soil reduction was suggested based on more extensive root damage and sulfide levels on roots observed in WS as compared with DS.