Abstract
Since 1961 through 1971, this study was conducted to determine the distribution of the replaceable 90Sr in loam surface soil originated from volcanic ash under three kinds of soil management, i. e. clean, mulch and sod systems at a citrus orchard.
The level of the replaceable 90Sr in the surface soil measured in 1963 was in the order of clean(41) ÷ sod(40) > mulch (31 nCi/m2·(0—30 cm)) and decreased exponentially with a half-time of approximately 5.9, 12.3 and 10.2 years for clean, mulch and sod systems, respectively. It was observed that the distribution coefficient of 90Sr calculated for these soils depended largely on the replaceable 90Sr content in surface soil and that the level of the coefficient in the soil under each soil management system in 1971 was nearly equal to that in 1961. The distribution coefficient of three systems are in order of clean < sod < mulch.
