2024 Volume 93 Issue 4 Pages 278-293
In recent years, the yield of Tanba black soybeans has declined notably in Tanba-sasayama city. To address this issue, we explored the multifaceted effects of climate change on seed yield. We utilized historical data in plots where yields are investigated annually in Tanba-sasayama city, employing the FAO56 model with the Agro-Meteorological Grid Square Data, NARO for soil moisture estimates, alongside trend analysis, variable selection with Least Absolute Shrinkage and Selection Operator (LASSO), and Structural Equation Modeling (SEM) to uncover the causal relationships impacting yield. The estimations based on measured soil physical properties, crop calendars, and the Agro-Meteorological Grid Square Data, demonstrated the efficacy of the FAO56 model in predicting soil moisture for the studied plots. Trend analysis showed significant decline in seed yield and the ratio of whole seeds. Conversely, we observed an increase in the ratio of off-grade seeds. An intriguing finding was the role of increased solar radiation in late October, which significantly contributed to the negative trends in seed yield and the rise in the ratio of off-grade seeds. Further insights from LASSO and SEM analyses highlighted early October soil moisture as a critical factor for seed yield variability. This suggests that seed yield may be effectively enhanced by optimizing the irrigation schedule. These findings will be useful for improving the cultivation techniques and developing a climate-resilient production system to counteract the reduction of yield in Tanba black soybeans, thereby contributing to the future sustainability of Tanba black soybean production.
