土壌化学性

Soil chemical properties of the surface horizon were compared between paddy, upland and orchard fields by conducting factor analysis on analytical data for agricultural lands of Saga and Kumamoto prefectures. Soils of Saga prefecture were mainly derived from alluvial marine or fluvial sediment in the paddy field and from granite or andesite in the orchard field. Factor analysis for agricultural lands of Saga prefecture reduced 11 variables (pH, total carbon and nitrogen, cation exchange capacity, exchangeable Ca, Mg and K, base-saturation percentage, phosphate absorption coefficient, and available phosphate and nitrogen) to three common factors having the eigenvalues larger than 1 with 70 to 80% of cumulative percent of total variance. The three common factors were termed texture, soil reaction, and organic matter content, common to both paddy and orchard fields, based on the factor loading matrix after varimax rotation. In the paddy field, more variables were correlated to the texture factor than to the soil-reaction or organic-matter-content factor. On the other hand, more variables were correlated to the soil-reaction or organic-matter-content factor for the orchard field which is under the intensive management. Soils derived from volcanic ash were selected for factor analysis of agricultural lands (paddy and upland) of Kumamoto prefecture. First three common factors showed the eigenvalues larger than 1 with 72 to 85% of cumulative percent of total variance. The common factors were termed soil solution concentration, soil reaction, and organic matter content. The soil-solution-concentration factor, in stead of the texture factor in the Saga soils, is associated with the very low solid-volume percentage (in the order of 20%) of volcanic-ash derived soils. The variables such as exchangeable Ca, Mg and K, and available phosphate and nitrogen of the Kumamoto soils were correlated to the soil-solution-concentration or soil-reaction factor and not to the organic-matter-content factor. No essential difference was observed between paddy and upland fields.