A proposal for the new soil classification of farmland in Kochi, Japan
1998
Kawazu, H. (Kochi Univ., Nankoku (Japan). Faculty of Agriculture) | Ota, I. | Sakurai, K.
Soils in the farmland1and (reclamated upland field, upland crop field, and drained paddy field for upland crops) and the forest in Kochi, Japan were classified with the new set of variables including the data on conventional soil fertility plus charge characteristics and oxides contents. Furthermore, the soils were Classified based on the total chemical composition and also on the water soluble fractions. All of these trials are to establish an appropriate classification system of farmland with highly variable history of land utilization. The following four systems were investigated: a) soil classification by the conventional soil characteristics (8 variables) was easily affected by the current soil management and/or fertility management. Thus, it could not be regarded as a proper method for the soils with a various land use history. b) In addition to system a), four new index values (zero point of charge (ZPC), sigma(p) (remaining charge at zpc), dithionite - citrate - bicarbonate soluble Fe, acid - oxalate soluble Al) were used (12 variables). Newly added indices could be considered as the properties which are not affected easily by the soil and fertility management. This system resulted in an appropriate soil classification to differentiate the various land use history. c) Soil classification using 10 mineral components of the soils reflected the properties of the parent materials and their weathering condition. However, the applied fertilizer was also found even in the subsurface soils greatly. d) Soil classification using water soluble fractions (anions, cations, low molecular weight organic acids, 15 variables) was mostly based on the amounts of them, and therefore, only the current soil management was reflected on this system
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