Abstract
The objectives of our study were : (1) To investigate the feasibility of using the digital KFA 1000 imagery analysis as a means of accurately describing and quantifying soil properties of Andosols, and (2) to reveal the relationship between the soil properties and the extent of clubroot disease incidence in cabbage. The film (Sojuzkarta #25253, scale 1 : 250, 000), acquired on June 7, 1988, was used to examine the approach in the entire area of Tsumakoi-mura of Gunma Prefecture. The film is sensitive in the red (570-680 nm) and near infrared (680-810 nm) regions. The scanner data were converted from analog to digital from by a drum scanner with a 25-μm sampling pitch. This method provided data with a pixel size of approximately 6 m×6 m. The near infrared reflectance was a better indicator for delineating five soil series than the red reflectance, indicating the differences of soil color, organic matter content, and water regime among the five soil series. The large variations in the red reflectance within a single soil series may be influenced by different soil moisture conditions ; five soil series and three drainage classes were identified. The effect of soil series on the retardation of the disease incidence was much greater in Light-colored Andosols than in other types. The disease was more severe in the poorly drained class. A season of abundant rainfall was shown to increase the incidence of the disease. Sojuzkarta KFA 1000 imagery provides good information on soil properties of Andosols for the assessment of the incidence of clubroot disease.
