Abstract
The cool and wet summer of 1993 in Tokachi district, Hokkaido, Japan, resulted in damage to sugar beet and caused an overall reduction in yield. Landsat/TM and Mos-1/MESSR images were analyzed for detecting the location and extent of the damaged area. Data for the period of July to September 1993 (alow-yield year), were compared to data for August 1991 (a bumper year).
Yield estimation equations for 1991 and 1993 derived from Landsat/TM data taken on August 29 1991 and those on July 8 corresponded with actual yield. Results showed severe damage in the fields with low soil organic matter. The change in KVI (vegetation index) values was small in July, medium in August and medium in September. No damaged fields were found in the area with higher soil organic matter. In these areas the KVI value was medium in July, high in August and low in September.
The relationships amcng the extent of the damage, the changes of KVI, and soil organic matter content suggested that the production drop was partly due to leaching of fertilizer by high precipitation in addition to damage from the cool and wet summer.
