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Is Wheat Yield Truly Low in Japan?: Examining Yield Formation Efficiency in Comparison With Northwest Europe

Shoko Ishikawa,Takahiro Nakashima,Martin C. Hare,Peter S. Kettlewell

Published 2025 in Food and Energy Security

ABSTRACT

From a perspective of food security, the agricultural sector worldwide has a responsibility to improve crop yields. Wheat yield in Japan is about half that of high‐yielding countries in Northwest Europe. Explanations offered so far—such as high temperatures and a rainy summer season shortening wheat's growth period, or comparatively underdeveloped breeding and cultivation techniques—remain speculative. This lack of clarity risks misdirecting research efforts on wheat cultivation in Japan and possibly other parts of the world. To address the issue, the present study focused on the efficiency of yield formation, rather than yield itself, across Japan and Northwest Europe. The efficiency of yield formation, derived from the division of actual yield by sunshine hours during the specific growth period from ear emergence to maturity, was compared between two geographical regions while factoring in climate variables. Despite the large yield difference, there was no significant difference in the efficiency of yield formation of wheat between the two regions. This indicates that Japan's low yield is largely due to climatic adversity for wheat, that is, high temperature, high precipitation and short sunshine hours during the critical growth phase for yield formation of the crop. The implication is that improvements in breeding and cultivation techniques alone are not likely to significantly increase wheat yield in Japan. A fruitful direction for future research endeavors in wheat production in monsoon Asia was discussed.

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