2024 Volume 95 Issue 1 Pages 11-20
This study aimed to assess areas of poor water retention within agricultural fields by examining the relationship between satellite images, topography, and soil water retention in the Tokachi and Okhotsk districts of Hokkaido, Japan. Areas with a lower normalized difference vegetation index (NDVI) during both the young panicle formation and maturation periods of winter wheat fields were found to have a higher sand content, a shallower gravel horizon, and lower levels of easily available water and autoclaved nitrogen contents (NAC) compared to the control area. These conditions, indicative of poor water retention and low NAC, could hinder initial growth and accelerate the maturation of winter wheat, resulting in a lower NDVI. However, NAC levels were found to vary spatially in some fields that had different topographies or management histories, and this variability influenced the NDVI. Additionally, the presence of weeds could potentially affect the NDVI within a field, even if the water retention was consistent. In conclusion, areas of poor water retention can potentially be identified by areas with a lower NDVI during both the young panicle formation and maturation periods of winter wheat. This is applicable if the field is free from weeds, pests, and diseases, has a consistent management history, and is located on unique topography.