Pedologist

The volcanogenic dark red soils are distributed in the Minamikushiyama-cho, Unzen City, located in the southwest of Shimabara peninsula. These soils developed on the decayed basalts. In the Uwaba plateau, Higashi-Matsuura Peninsula in the north of Saga, decayed basalts are called the "Onjaku", while, in this study area, there are the materials similar to "Onjaku" originated from Suwanoike Basalts of ca. 600 ka. Chemical and physical properties of volcanogenic dark red soils were similar to the soils originated from the "Onjaku" of Uwaba plateau. It is thought that the volcanogenic dark red soils in this study formed from the materials similar to "Onjaku" as parent material. These soils contained a lot of hematite having high crystallinity and large crystal size. This showed that lava of basalt caught reaction by hydrothermal alteration, or an oxidation state of basalts changed at the time of cooling of lava. It is estimated that the soil particles of surface layer in this soil profile become gradually finer and clayey by weathering. Also the soils were formed by erosion, addition of aeolian dusts, and supply of organic matter by growing of some vegetation. It was effective for the classification of volcanogenic dark red soil to identify hematite by using X-ray diffraction analysis of non-treated air-dry fine soil so that Mitsuchi (1985) pointed it out.

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This study evaluated the influences of various land uses on mineralogical properties and charge characteristics, and discussed the availability of these properties as a tool that can assess the potential of the soils in terms of long-term productivity. Thirty study sites, which are located in the upland area of Lower Northern Thailand, were selected including cropping lands and fallow forests under shifting cultivation systems, fruit and mixed tree plantations and natural forests. Soil samples were collected from the surface and subsurface layers before and after burning practice. Most of the soils in the village were classified into Typic Paleustults. The soil fertility level widely varied among land use types. The PZSE values were constant irrespective of land use types. Whereas σ_p values was not related to land use types. Kaolin minerals were predominant among clay minerals in the study area associated with occurrence of weatherable 2 : 1 type clay minerals. The conventional chemical properties were affected by burning practice. On the other hand, sesquioxide properties and clay mineral compositions did not change by burning practice. The conventional measurements are useful for assessment of the current crop management. While the use of the charge characteristics and mineralogical properties seem to be beneficial to evaluate long-term productivity, because these properties are rather stable against the impact of various agricultural practices.

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To clarify the factors affecting nitrification with nitrogen applied as high concentration, incubation experiments were conducted. Twenty-two soil samples obtained from arable lands in Hokkaido, more than half of which were Andosol, were used for incubation experiments. Addition of ammonium phosphate to the 22 soils at a rate of 0, 50, 100, 200, 300 mg N kg^<-1> and incubation for 14 d revealed that; (1) The higher concentration of added-N suppressed relative percent nitrification. (2) Comparing the 22 soils about nitrification at the highest amount of added nitrogen (300 mg N kg^<-1>), in the higher-organic matter soil (Haplic Andosol, total carbon content was 31.4-82.4 g kg^<-1>), percent nitrification was faster, than in the other lowerorganic matter soils (total carbon content was; Haplic Volcanogenous Regosol 13.6-25.8 g kg^<-1>, Low-humic Andosol 10.1-24.7 g kg^<-1>, Haplic Brown Lowland soil 9.3-12.5 g kg^<-1>). (3) Within the Haplic Andosol, nitrification was significantly associated with soil pH. (4) As for all 22 studied soils, percent nitrification was significantly associated with total carbon content firstly, and secondly associated with soil pH. Ammonium sulfate, ammonium phosphate, and urea (all 300 mg kg^<-1>) added to one soil with a relatively higher carbon content and pH were nitrified completely in 42 d. When added at 500 and 1000 mg N kg^<-1>, however, nitrification of these forms was suppressed; the percent nitrification was the lowest in ammonium sulfate, followed by ammonium phosphate and urea. Based on these results, applied nitrogen concentration, soil carbon content, soil pH, form of nitrogen source, and their interactions are factors that affect nitrification. These findings have implications for improving nitrogen fertilization.

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In last 50 years, the soil survey in Taiwan have great contribution on the soil database and good interpretation on soil management, fertilizer recommendation, and environmental quality, especially on the soil survey in detailed soil survey of Taiwan rural soils (1962-1976, 1974-1979), detailed soil survey of Taiwan hill land (1980-1988), detailed survey of contaminated soils (1984-2000), soil survey of productivity grade of Taiwan upland (1986-1990), detailed soil survey of Taiwan forest soils in Mountains (1993-2002), detailed grid soil survey of Taiwan rural soils (2000-2010), and Soil quality monitoring (1997-2007). More systematic and series studies by the pedologists in Taiwan in the last 50 years major include the soil characteristics and genesis of soils derived from different parent materials (1960-1975), rice-growing soils (1980-2005), Podzolic soils (1988-2005), and volcanic soils (1990-2005). There are always about 20 pedologists were doing the national soil survey projects from 1974 to now, and there are only 10 to 15 pedologists are working in TARI and different Universities of Taiwan in last decade. Now, we are facing to develop the new strategies of soil survey for the future. The major items will be discussed, including develop the new soil survey techniques for identify the boundary of contaminated soils, using the national soil information system for more soil interpretation, provide a regional soil museum to strength the soil function education, revise the regulation of nutrients or pollutants for maintain the soil quality, crop quality, and environmental quality, and finally to decide which direction we can go.

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