Sadao Shoji

Active aluminium and iron in the humus horizons of andosols from northeastern Japan: Their forms, properties and significance in clay weathering

We studied the forms, properties, and significance of active Al and Fe in the humus horizons of Andosols from northeastern Japan and formed a hypothesis to elucidate the surface weathering of volcanic ash. Our soil samples were divided into two groups: nonallophanic and allophanic. Nonallophanic soils showed that Al of weathering products is present in major amounts in 2:1 layer silicates and in minor amounts in Al-humus complex. The Fe of weathering products, however, consisted mainly of the “free”form, which is largely complexed with humus. A small portion of this element was contained in the layer silicates. The Al of weathering products in allophanic soils was found in large amounts in allophane and imogolite and in small amounts in allophanelike constituents and Al-humus. The Fe of weathering products in these soils consisted wholly of “free” Fe, which is partly complexed with humus. We indicated that the formation of Al- and Fe-humus complexes, allophane, and imogolite is governed by soil acidity to a great extent. Formation of Al- and Fe-humus complexes proceeded with decreasing pH(H2O). The formation of allophane and imogolite took place in the pH(H2O) >4.9, however, and had an inverse relationship with formation of the Al-humus complex. The nonallophanic and allophanic soils, with a few exceptions, showed pH (NaF) values >9.4 and large phosphate absorption. We noted that the active components of Andosols show a wide variation in their contribution to unique chemical properties of the soils. In order to bring nonallophanic Andosols into Andepts, we emphasized the necessity of redefinition of “amorphous material.” Finally, based on our present and previous studies, we showed a new weathering scheme for volcanic ash in modern humus horizons.

Use of polyolefin-coated fertilizers for increasing fertilizer efficiency and reducing nitrate leaching and nitrous oxide emissions

This paper reviews some of the benefits of polyolefin-coated fertilizers (POCFs) with accurate controlled release properties. They are helpful in developing innovative rice farming systems, such as no-till direct seeded rice with single basal fertilization and transplanting of rice seedlings with single basal fertilization. These new cultivation systems can increase fertilizer efficiency and reduce farming costs. The recovery of basal N can be increased from 22–23% with conventional broadcast application of ammonium sulfate or urea to 79% withco-situs application of polyolefin-coated urea. The no-till rice cultivation of transplanting of rice seedlings with single basal application of POCFs decreased the farming cost by 65% as compared to that of the conventional rice cultivation. Theco-situs application of POCFs containing NPK reduced nitrate leaching and nitrous oxide emissions from cultivated soils with heavy fertilization. Since POCFs have various nutrient composition and release types, a variety of application methods to agricultural and horticultural plants are being developed in Japan.

CHEMISTRY AND CLAY MINERALOGY OF ANDO SOILS, BROWN FOREST SOILS, AND PODZOLIC SOILS FORMED FROM RECENT TOWADA ASHES, NORTHEASTERN JAPAN

We conducted chemical and clay mineralogical studies on Ando soils, Brown forest soils, and Podzolic soils that had been formed mainly from felsic Towada-a (1000 B.P.) and Chuseri (4000 B.P.) ashes under different climates and vegetation. Organic carbon accumulated remarkably in the humus horizons of all the soils and contributed to the high CEC of the soils. Soil acidity was observed to be in the order of Ando soils < Brown forest soils < Podzolic soils, reflecting the differences in base saturation and clay mineralogy of these soils, and to have a tendency to decrease with depth within the same profiles. Diagnostic properties of soil samples, such as pH(NaF), phosphate absorption, pyrophosphate-soluble Fe(Fep)/dithionite-citrate-soluble Fe(Fed), pyrophosphate-soluble Al(Alp)/dithionite-citrate-soluble Al(Ald), Fep + Alp/percent clay, Fep + Alp/Fed + Ald, etc., were studied in detail. None of these chemical criteria, however, could distinguish satisfactorily among Ando soils, Brown forest soils, and Podzolic soils formed from Towada ashes. It was noted that both Fep/Fed and Alp/Ald ratios increase with decrease in the soil pH(H2O). Notable differences in clay mineralogy were observed between soil groups. Ando soils had mostly clay fractions dominated by amorphous materials consisting mainly of allophane and imogolite. Nonexpansible chloritized 2:1 mineral, which was major among the crystalline clay minerals, was present in relatively large amounts only in the surface horizons. Brown forest soils showed a diversity in clay mineralogy within the same soil profiles. The clay fractions of the surface soils showed an abundance of chloritized 2:1 mineral with high expansibility and an absence of allophane and imogolite. The subsoils showed major amorphous and paracrystalline materials with minor 2:1 layer silicates. The clay fractions of the Podzolic soils, except those of IIB horizon soils, were characterized by the abundance of chloritized 2:1 mineral varying widely in expansibility and by the absence of allophane and imogolite. The IIB horizons from Chuseri ash had clay fractions dominated by amorphous materials consisting mainly of free iron and alumina. Laminar opaline silica was found in almost all the humus horizons and was relatively abundant in the modern humus horizons of Brown forest soils. We concluded that formation of allophane and imogolite, as well as chloritization of 2:1 layer silicates, is related primarily to soil acidity. Allophane and imogolite formed only in the soils having pH(H2O) >4.9, irrespective of differences in soil groups and soil horizons. The 2:1 layer silicates were considered to have formed largely by alteration of volcanic glass. Chloritization of 2:1 layer silicates was observed to proceed with formation of allophane and imogolite. The formation of laminar opaline silica in the surface soil was considered to be suppressed not only in the Ando soils containing large amounts of allophane and imogolite, but also in the Podzolic soils, which are subject to strong leaching.

Properties Of Nonallophanic Andosols From Japan

We studied various properties of nonallophanic Andosols in Japan. Our results showed that, despite many similarities between nonallophanic and allophanic Andosols, significant dissimilarities also exist between the two groups of soils. The nonallophanic Andosols used for our study formed from rhyolitic, dacitic, or andesitic volcanic ash in a humid temperature climate. They had distinctive morphological properties common to allophanic Andosols in Japan: (1) very dark, thick humus horizons, (2) granular structure in the humus horizons, (3) friable to very friable consistence, and (4) abrupt or clear smooth boundaries between humus and nonhumus horizons. The clay mineralogy of the nonallophanic Andosols was very different from that of the allophanic Andosols. In nonallophanic Andosols the clay fractions are mostly dominated by chloritized 2:1 minerals and the active Al (acid-oxalate-ex-tractable Al) consists largely or wholly of Al complexed with humus (pyrophosphate-extractable Al). The nonallophanic Andosols had mostly medium to fine textures and considerable high water retention at 15 bars. We noted that these soils have characteristically low bulk density, which is closely correlated with the organic carbon content. A remarkable accumulation of humus took place in the nonallophanic Andosols and was closely correlated with the formation of Al-humus complex. The high CEC of these soils was ascribed to the high humus content. We noted that nonallophanic Andosols are strongly acid to very strongly acid, reflecting the abundance of chloritized 2:1 minerals and the very low base saturation. Therefore, they had high Al saturation and large amounts of KCl-exchangeable Al, which is a major deterrent to plant growth in the soils. The average values of Al saturation and KC1-ex-changeable Al were 74.4% and 5.51 meq/ 100 g for humus horizon soils and 59.8% and 3.50 meq/100 g for nonhumus horizon soils, respectively. Almost all the nonallophanic Andosol samples had pH (NaF) >10 and phosphate retention > 85%. These values were significantly correlated with the acid-oxalate-extractable Al (Alo). Soils containing > 1% Alo have pH (NaF) > 9.4 and phosphate retention >85%. Therefore, we noted that Al complexed with humus has a significant amount of OH groups and is highly reactive. The analysis of pyro-phosphate-soluble components indicated that the humus associating with Al and Fe consists largely or wholly of humic acid with the highest degree of humification.

Evaluation and proposed revisions of criteria for andosols in the world reference base for soil resources

The proposed criteria for Andosol classification in the World Reference Base (WRB) of Soil Resources were evaluated using the Tohoku University World Andosol Database (TUWAD). The WRB proposal defines a diagnostic andic horizon comprised of vitr-andic, alu-andic, and sil-andic subtypes, and eight

PLANT ROOT GROWTH IN ACID ANDOSOLS FROM NORTHEASTERN JAPAN: 2. EXCHANGE ACIDITY Y1 AS A REALISTIC MEASURE OF ALUMINUM TOXICITY POTENTIAL

Chemical and greenhouse studies were conducted to show that exchange acidity Y1, determined by titration of 125 ml of N KC1 soil extract (soil:N KC1 = 100:250) with 0.1 N NaOH, was a useful, realistic measure of aluminum toxicity potential in acid Andosols from northeastern Japan. Twenty-eight soil samples consisted of allophane-imogolite soils (11 samples; pH(H2O) 4.6 to 5.9, Y1 0.4 to 3.1 ml/100g), chloritized 2:1 mineral soils (13 samples; pH(H2O) 3.9 to 5.0, Y1 6.8 to 38.2 ml/100g), and allophane-imogolite-chloritized 2:1 mineral soils (4 samples; pH(H2O) 4.6 to 5.3, Y1 3.3 to 5.0 ml/100g). Three test plants, burdock cv. Takinogawa (Arctium lappa), barley cv. Norin-24 (Hordeum vulgare), and dent corn cv. Choko-1 (Zea mays), were grown on these soils in a greenhouse, and their root length and acid-injury were observed. Root length of all the test plants had a significant relationship with exchange acidity Y1, shown by exponential equations. Degrees of acid-injury determined by root length and root morphology were also closely related to exchange acidity Y1. Chloritized 2:1 mineral Andosols had “critical” pH(H2O) of about 5.0 and “critical” pH(KCl) of about 4.5, whereas allophane-imogolite Andosols did not have these “critical” pHs and did not restrict the root growth greatly even at low pH(H2O), such as 4.6. Acid substances relating to exchange acidity Y1 were found to consist mainly of Al3+ ions whose amount was closely correlated with total exchangeable Al. A comparative study of exchange acidity Y1, pH(H2O), pH(KCl), fluoride-reactive Al, etc., showed that exchange acidity Y1 was a useful realistic measure of aluminum toxicity in the acid Andosols.

AN EXAMPLE OF ANDOSOLIZATION AND PODZOLIZATION AS REVEALED BY SOIL SOLUTION STUDIES, SOUTHERN HAKKODA, NORTHEASTERN JAPAN

We examined soil-forming processes along a climobiotic transect in the southern Hakkoda Mountains of northeastern Japan. The soils have developed on the same volcanic ashes that were deposited approximately 1000 and 5000 B.P., In Japan, chemical and morphological criteria based on the solid phase fail, in some cases, to distinguish between Spodosols and Andisols formed in volcanic materials. This problem also occurred along the transect examined in this study; however, collection and analysis of ecosystem waterflows, which included soil solutions, canopy throughfall, and precipitation, have allowed documentation of current soil-forming processes. Podzolization was found to be active in the subalpine Abies mariesii-Sasa kurilensis ecosystem. Iron, Al, and dissolved organic carbon were mobilized from the A horizon and became arrested in the Bw horizon. In contrast, andosolization dominated soil formation in the Miscanthus sinensis grassland ecosystem. This process was characterized by an accumulation of Fe, Al, and dissolved organic carbon in the A horizon with little subsequent leaching of these components into the B horizon. Formation of B horizons under both soil-forming processes appears to be dominated by in situ weathering rather than illuviation.

Physical And Chemical Properties And Clay Mineralogy Of Andosols From Kitakami, Japan

Physical and chemical properties and the clay mineralogy of Normal and Light-Colored Andosols from Kitakami, Japan were studied. The profiles of both Andosols had features reflecting the repeated falls of tephras with different ages. The Normal Andosol, which is a common Andosol in Japan, showed unique properties, such as large total porosity, high water retention, low bulk density, remarkable accumulation of organic matter, high fluoride pH value, large phosphate absorption, etc. The Light-Colored Andosol, which was formed by truncation, also had some of these unique properties. It was noted that chloritized 2:1 minerals were dominant, and allophane and imogolite were absent in the clay fractions of all the soil samples derived from volcanic ash, whereas allophane and imogolite were dominant in the clay fractions of all the soil samples from pumice. It had been assumed that the unique physical and chemical properties of a common Andosol were largely attributable to the high content of allophane. The results obtained in this study show, however, that most of the unique properties of the Andosols from Kitakami are closely related to the dithionite-citrate-soluble constituents, especially alumina, to a great extent.

Properties of Spodosols and Andisols showing climosequential and biosequential relations in southern Hakkoda, northeastern Japan

We conducted comparative studies on the chemical and mineralogical properties of selected pedons of Spodosols (Placorthods) and Andisols (Fulviudands and Melanudands) derived from Towada-a ash of 1000 B.P. and Chuseri ash of 5000 B.P., Spodosols and Fulviudands of the climosequence showed most remarkable differences in such chemical properties as soil acidity, fluoride and phosphate reactivity, humus accumulation and composition, and clay mineralogy, chiefly in noncrystalline aluminosilicates. Fulviudands and Melanudands, however, having a biosequential relation, showed contrasting differences mainly in the properties of soil humus. Spodosols showed remarkable accumulations of Fe and Al and also displayed the existence of placic horizon. Nevertheless, one of the two Spodosols did not meet the chemical criteria for a spodic horizon. Both Andisols and Spodosols satisfied the andic properties. In this paper we also discuss Spodosol-Andisol transition problems and propose some solutions.

Growth and chemical composition of Japanese pampas grass (Miscanthus sinensis) with special reference to the formation of dark-colored Andisols in northeastern Japan.

Abstract We studied the growth and chemical composition of Miscanthus sinensis in various locations showing significant differences in climate, elevation, and properties of Andisols in northeastern Japan. Accumulated effective temperature above 10°C (AET) was found to be a very useful index to analyze the relationships between climate and plant growth such as plant height, leaf number, and dry matter production. M. sinensis ecosystems occurring at the upper limits showed almost the same minimum leaf number (12-13) and AET (26-29) in all the study areas. The plant produced large amounts of organic matter not only in the aboveground part but also in the underground part. The contents of plant mineral constituents were determined during the growing season. No minerals except Al showed variations in content depending on yearly changes in climate and differences in soil conditions. The mineral uptake per unit area was large for K and Si, medium for N, low for P, Ca, and Mg, and very low for Al. Finally we disc...