Effect of Light Environment Differences on the Paddy Rice Yield in the Mountainous Area

Abstract

The purpose of this study is to clarify effects of light environment differences due to the complex topography in the mountainous areas on paddy rice yield. The relationships between paddy rice yield (Koshihikari BL) and meteorological environments, especially light condition, were investigated in the Higashi-shimogumi district, Tokamachi City, Niigata Prefecture for three years. The results show that no significant difference in yield was found between two fields with different light environment. As a factor, total number of paddies per 1 m² (sink ability) was significantly positively correlated with the cumulative PPFD during the 60 to 30 days before heading, 2) the photosynthetic ability of individual leaves in the lower-light filed was increased due to the adjusting function against lower-light condition, 3) canopy's sink ability in higher-light field was greater than that in lower-light field and the assimilate production to satisfy sink was not enough, resulting ripening rate in higher-light field was lower than that in lower-light field. These results will assist in the model development for predicting rice yields in mountainous regions and agricultural technologies that make us of diverse weather conditions.