Effects of Climatic Factors on Rice Yield in Japan: Analysis of Morphological Traits and Dry Matter Production

Abstract

Rice yield in Fukuoka prefecture, which is a warmer region, was compared with that in Akita prefecture, which is a colder region in Japan, using the main varieties “Hinohikari” and “Akitakomachi” used in these regions, respectively. Although days from transplanting to heading in“Hinohikari” in the warmer region were shorter than in “Akitakomachi” in the colder region, the mean solar radiation and mean temperature from 30 days before heading to 30 days after heading was higher in “Hinohikari” than in “Akitakomachi”. The length of leaf blade was longer and the top dry weight and leaf area at the full heading stage were larger in “Hinohikari” than in “Akitakomachi”. The total spikelet number per area was not different between the two varieties, but the percentage of ripened grain was lower in “Hinohikari” than in “Akitakomachi”. As a result, the yield was lower in “Hinohikari” than in “Akitakomachi”. On the other hand, in the statistical survey on crops, the yield was lower in Fukuoka prefecture, than in Akita prefecture, since both the total spikelet number per area and the percentage of ripened grain was lower in the former. These results suggest that the higher temperature before heading restricts the total spikelet number per area and/or the higher temperature after heading reduces the ability of ripening, resulting in the lower yield in Fukuoka prefecture, which has a warmer climate.