Environmental and Agricultural Significance of Volcanic Ash Soils

Abstract

　Volcanic ash soils begin to form with rapid restoration of vegetation soon after ash deposition and create a productive and comfortable environment. They also have various important functions such as accumulation of large amounts of organic carbon and nitrogen, plentiful storage water, water quality improvement, and preservation of paleoenvironment and archaeological artifacts. 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. The properties relating to their soil productivity are comprehensively described. In order to solve the serious problems caused by unsuitable management and to sustain volcanic ash soils, crop rotation, soil improvement, and precision agriculture and programmed fertilization are encouraged. Recommended rotations for with high economic advantages also include crops to control soil-borne diseases and nematodes, gramineous plants to enhance soil organic matter levels and crops having symbiotic interactions with arbuscular mycorrhiza that promote plant uptake of soil phosphorus. Some volcanic ash soils have soil horizons that strongly inhibit plant root development. Soil improvements such as deep cultivation and soil mixing are practiced for such soils. Programmed fertilization using controlled-release fertilizers with high performance is recommended especially for intensive agriculture on small-scale fields. Correctly programmed fertilization can be conducted at the best site by single basal application for most crops in Japan. With proper management volcanic ash soils are capable of high productivity and long-term agricultural and environmental sustainability.