Volcanic ash soils are among the most productive soils in the world. Nowadays they are most extensively utilized for growing high-value horticultural crops in Japan. ... With proper management volcanic ash soils are capable of high productivity and long-term agricultural and environmental sustainability.
(from Environmental and Agricultural Significance of Volcanic Ash Soils by Sadao Shoji and Tadashi Takahashai)
Sitting in the midst of Kumamoto Prefecture is the Mt Aso Volcano. The Volcanic ash provides the entire area with a highly productive growing environment. Not surprisingly, products grown and produced in Kumamoto are rich in nutrients and high in flavor.