Grain yield disparity of rice between tropical and subtropical/temperate Regions

Enhancing productivity of rice (Oryza sativa L.) is a need to meet the food demand of increasing population. Rice, being the main staple for more than half of the world’s population, is grown in a wide range of environments under a variety of climatic conditions covering tropical, subtropical and temperate regions in the world. Some scientists attribute the comparatively higher grain yields of rice in developed countries such as Australia, USA, Japan and China in the subtropical/temperate region to the technological improvements, without disclosing precise technological gaps for yield disparity, while ignoring the influence of climatic- and soil-related differences of the regions. Studying the influence of climate and soil characteristics on rice yield disparity between tropical and temperate/subtropical regions is important to avoid erroneous conclusion given in explaining any yield disparities. Existing grain yield disparity of rice between the two regions can mainly be attributed to environmental factors such as incident solar radiation, temperature and soil fertility, but not to the improved technology. In Sri Lanka, the influence of technological advancements on the grain yield resulting in yield disparities compared to other developed countries as indicated by some critics, is irrelevant and invalid owing to confounding effects of the environmental factors. If a fair comparison to be made on grain yield disparity of rice between countries, they have to be within the same region, i.e. tropical or subtropical/temperate, where the climatic- and soil-related factors are fairly uniform.