Abstract
The purpose of this study was to understand the regional differences of crop productivity and their future prediction in Memuro Town, located in the central Tokachi region, Hokkaido. We analyzed the relationship between the yields of sugar beet roots and soil type (Brown Lowland soils, Brown Lowland soils with a volcanic ash surface, Andosols and Wet Andosols) obtained via the method of Niwa et al. (2008) and using meteorological data from AMeDAS for the surveyed area. In addition, the future differences of the root yields among soil types were predicted using the above relationship data and future climate prediction data from MIROC3.2-HIRES. The results can be summarized as follows: (1) The sugar beet root yields with respect to soil types from 1990 to 2007 were highest in Andosols. Therefore, as an index of the differences of root yield among soil types, the root yield ratio for Andosols was calculated for each soil. (2) The root yield ratios for Andosols can be explained at more than 65% for each soil by cumulative precipitation from late April to mid July. (3) According to MIROC3.2-HIRES, the average cumulative precipitation from late April to mid July for each decade (2011-2100) was predicted to be more than 200 mm. Therefore, the relationship between the root yield ratios for Andosols and the cumulative precipitation from late April to mid July were investigated for the years with more than 200 mm of cumulative precipitation during 1990-2007. As a result, a highly correlated negative secondary regression equation was obtained for each soil type. (4) Based on those regression equations and on future prediction data of precipitation, the average root yield ratios for Andosols were calculated for each decade from 2011 to 2100. When comparing the predictions to current levels until 2080, the ratios for Brown Lowland soil groups were higher, while ratios for Wet Andosols remained at the same level. However, after 2081, the average root yield ratios of both Brown Lowland soils returned to the same level as current ratios, while the ratios of Wet Andosols were predicted to be lower than the current level.
