2018 Volume 87 Issue 3 Pages 233-241
Although soybean production in the Tohoku region of Japan may be negatively affected by drought due to climate change, it is not clear how the production is affected by drought. In this study, the FAO56 evapotranspiration model was applied to an experimental field at the Kariwano campus of Tohoku Agricultural Research Center by using agrometeorological grid square data, and correlations of soybean yield and 100-seeds weight in a long-term continuous performance test over 33 years at the site with meteorological factors and soil volumetric water content (SWC) were analyzed. By using soil physic parameters such as field capacity, permanent wilting point and effective root layer, the time-course change of SWC during the growing season in the soybean field was well predicted by the FAO56 model. The seed yield and 100-seeds weight over 33 years showed significant negative correlations with air temperature and SWC averaged during August. Furthermore, the partial correlation between seed yield and average temperature of August was insignificant when SWC was used as a control variable, indicating that the yearly variations of seed yield and 100-seeds weight are mainly explained by the variation of SWC averaged during August. This means that drought caused the reduction of seed yield and 100-seeds weight. Thus, it was suggested that the FAO56 model combined with agrometeorological grid square data was effective for assessing accurately the effect of drought on soybean production in Japan.
