Argillic Horizons Research Articles

Atributos topográficos na diferenciação de Argissolos

A topografia do terreno controla muitos processos hidrológicos, geomorfológicos e pedológicos, influenciando a radiação solar, precipitação pluvial, escoamento superficial, evaporação, regime de umidade do solo e tipo de vegetação, entre outros. Desta maneira, atributos topográficos derivados de um modelo digital de elevação foram utilizados para explicar a diferenciação de solos com horizonte B textural da região de ''Mar de Morros'', no noroeste do Estado do Rio de Janeiro. Foram estudados oito perfis de solo (quatro Argissolos Vermelhos e quatro Argissolos Vermelho-Amarelos), desenvolvidos de granulitos noríticos nos municípios de São José de Ubá e Itaperuna. Os dados dos atributos topográficos em cada perfil de solo (elevação, declividade, aspecto, plano e perfil de curvatura, radiação solar e índice topográfico combinado) foram extraídos, utilizando-se uma janela de 7 x 7 pixels, com os perfis ocupando o centro dessa janela. Os Argissolos que ocorrem nas encostas noroeste e nordeste recebem maior quantidade de radiação solar (mais quentes e secas) e por isto são vermelhos, eutróficos e não apresentam horizonte B latossólico, enquanto os solos das encostas sudeste (relativamente mais frias e úmidas) são vermelho-amarelados, distróficos e com horizonte B latossólico. A radiação solar, a declividade e o aspecto são os atributos topográficos relacionados com as diferenças entre os perfis de solos estudados. Os atributos topográficos analisados pelas técnicas multivariadas apresentaram-se efetivos para a distinção entre os Argissolos Vermelho-Amarelos distróficos e os Argissolos Vermelhos eutróficos, exceto o P7 (PVe). Estudos relacionando a influência da radiação solar na pedogênese são escassos em condições tropicais e, embora menos atuante em regiões tropicais, foi a radiação solar que determinou diretamente a diferenciação dos solos da área estudada.

Soil Profile Arsenic Concentration Distributions in Missouri Soils Having Cambic and Argillic Soil Horizons

Understanding of the pedogenic pathways associated with arsenic (As) transformations in soil is important to understanding arsenic soil chemistry and discriminating between natural background and anthropogenic arsenic (As). Twenty-one soil series, some with multiple pedons, were assessed to determine if the As distributions in soil profiles exhibit discrete maxima that correspond to the presence of agrillic horizons. The majority of pedons exhibiting argillic horizon expression show a Fe-oxyhydroxide and As maxima corresponding precisely with the argillic horizon. Pearson correlation coefficients verify the close correspondence of Fe and As. Soil profiles having cambic horizons, and lacking argillic horizons, may also show As and Fe accumulations at soil depths. Some coarse-textured, well-drained to moderately well-drained Entisols and Inceptisols have Fe-oxyhydroxide accumulation in their cambic horizons, promoting As accumulation. Conversely, silty-textured and poorly drained to somewhat poorly drained Entisols and Inceptisols have C and Cg horizons that show somewhat uniform Fe and As concentrations throughout their soil profiles. Analysis of selected pedons having well-drained to moderately well-drained soil profiles demonstrates that clay fraction Fe and As concentrations are closely correlated and that the As and Fe concentrations are greater than those from the corresponding whole soil. The somewhat poorly drained Crowley pedon exhibited cohesive masses of Fe and Mn accumulation (sand separate) that had greater arsenic concentrations than those of the clay and silt separates. These pedogenic nodules with enhanced arsenic concentrations reveal alternative pathways involving arsenic transformation.

English

ix typical representative pedons viz., Rejental (P1), Parvatapur (P2), Algol (P3), Bilalpur (P4), Zaheerabad (P5) and Krishnapur (P6) of Zaheerabad Mandal in Medak district of Andhra Pradesh were studied for their morphological, physical and physico-chemical properties and their suitability to rice, sugarcane and potato cultivation. The soils are red to dark brown in colour, moderately acidic to neutral (pH-5.9 to 7.0), non-saline, shallow to deep in depth. Texture ranged from loamy sand to sandy clay loam in surface soils whereas sandy to clay in sub­surface with high sesquioxide percentage. Organic carbon, cation exchange capacity (CEC) and base saturation ranged from 0.04 to 0.57%, 12.0 to 38.0 c mol (p+)/kg and 30.2 to 78.6%, respectively. The dominance of exchangeable ions was in the order viz. Ca2+> Mg2+>Na+>K+. Soils were low in available nitrogen (N) and phosphorus (P), low to high in available potassium (K). The soils developed with argillic (Bt) horizon, they were classified as Typic Haplustalfs (P4, P5), Lithic Rhodustalfs (P2), Rhodic Kandiustalf (P3), Typic Rhodustalfs (P1, P6). Suitability for three crops P1, P3, P5 were moderately suitable (S2), P2, P4, P6 were marginally suitable (S3). For sugarcane; P1, P3, P4, P5 were moderately suitable (S2), P2, P6were marginally suitable (S3). For potato, P3, P5, P6 were marginally suitable (S3), Rejental, Parvatapur and Bilalpur- N P1, P2, P4 were not suitable (N). Key words: Characterization, classification, lateritic soil, land suitability, rice, sugarcane, potato.

Soil genesis along a Catena in Southwestern Iran: a micromorphological approach

In order to determine the role of topography and drainage condition on soil genesis, a micromorphological study was carried out along a catena in Kohgilouye Province, southwestern Iran. The catena in this study crosses the main physiographical units such as alluvial and colluvial fans, piedmont plain, plateau, river alluvial plain, and lowland. Seven representative soil profiles were described and studied accurately. Thin section observations, scanning electron microscope (SEM), and digital microscope studies were used in this study. The major contributing soil processes can be categorized as calcium carbonate leaching, clay eluviation, and formation of Fe-Mn oxides. Calcite depletion pedofeatures were the most striking aspect of the soil thin sections studied. In pedons that were located on more stable physiographic unit, a higher frequency of micritic calcite nodules was observed. The presence of needle-shaped calcite in aquic and non-aquic conditions throughout the soil profile suggests an appropriate broad range of pedoenvironmental conditions for the formation and stability of this mineral habit. The magnitude of calcite nodules that were impregnated with Fe-Mn oxides was higher in soils formed on more stable geomorphic units. Adjacent formation of needle-shaped calcite and cytomorphic calcite in some horizons may suggest the biogenic source of this mineral. In most thin sections of argillic horizons, clay films were cleared after a mild HCl treatment, suggesting masking of the clay coating by carbonates.

Study of a toposequence for variability in micronutrients from the moist subhumid Siwalik agro-ecological subregion of Punjab

A toposequence from the moist subhumid Siwalik agro-ecological subregion ofPunjab was studied for available and total micronutrient variability. The toposequence showed the least developed soils with only an A–C horizon sequence on steep slopes and a well-developed profile with an argillic horizon on moderate slopes. The soils consist of a variety of minerals and thus belong to the mixed mineralogy class. There were higher levels of DTPA-extractable micronutrients in the surface horizon than in the subsurface horizon due to their association with organic matter through chelation and adsorption. The surface horizons have relatively lower total micronutrient contents than the subsoil horizons. Soils from moderate slopes and lower terraces showed higher total micronutrients contents in the middle horizons, suggesting some redistribution of the constituents due to the illuviation process of pedogenesis. DTPA-extractable and total micronutrients showed an irregular increasing trend from the steep slope to the lower terrace soils. The DTPA-extractable micronutrients showed relatively greater variability (8–107%) than the corresponding total micronutrient contents (2–34%), suggesting the relatively dynamic nature of the former. Variability in DTPA-extractable and total micronutrients within and among the different soils was caused by several processes involved in the differentiation ofmicronutrients. DTPA-extractable micronutrients show the influence of organic matter through the processes of chelation and adsorption, whereas total micronutrients varied due to differences in pedogenic processes of eluviation/ illuvial on different landscapes and textural variation.

Distribution and Origin of Argillic Horizons across Iowa-A Novel Hypothesis

Argillic horizons are common in most of the 48 contiguous states of the United States. In Iowa, soils with argillic horizons cover 33.5% of the land area. Fifty-nine percent of the area in Iowa with argillic horizons is in Alfisols (Udalfs and Aqualfs). The remaining 41% is in Argiudolls, Argiaquolls, and Argialbolls. At the county level, the prevalence of argillic horizons varies widely. We hypothesize that the presence of argillic horizons in Iowa is largely a function of these controls in some closed depressions (prairie potholes): (i) Si consumption by hydrophytic organisms, and (ii) prevalence of CaCO₃ and secondary Ca minerals. All controls are predicated on catena drainage. Our methodology was to compile pedologically relevant data and pedon descriptions from a variety of databases and use GIS to facilitate spatial interpretations. Our findings agree with the concept that mature forest and prairie catenas in open drainage systems generally have soils with well-expressed argillic horizons across an entire soil catena. In contrast, soils in catenas in closed drainage systems very rarely have argillic horizons and where they do, they are Argialbolls. The biotic (i.e., active pedogenic factor) contrast between the open and closed catenas appears to be the prevalence of Si hyper accumulators such as reeds (Sparganium eurycarpum), sedges (Carex stricta), cattails (Typha latifolia), diatoms, and sponges. Also, calcareous conditions in closed catenas preclude clay translocation, and promote formation of calcium silicate which is a passive sink for Si.

Mercury concentration in some calcareous soils of western Iran with a focus on pedological evolution and weathering process

The aim of this study was to evaluate total mercury concentration and its lithogenic and exogenic fractions in some calcareous soils of western Iran, where water contamination and bioaccumulation of mercury have been reported in the bottomland’s reservoir. In particular, we investigated soil physico-chemical properties and weathering conditions related to lithogenic and exogenic fractions of mercury for two groups of calcareous soils with a known comparative pedological evolution and weathering condition that was evident in the presence or absence of underlying layers of accumulated clay. Our results showed that the total mercury content of the studied soils ranged from 45.40 to 830.36 with a mean of 486.81 μg kg−1. Furthermore, calculation of mercury fractions revealed that lithogenic and exogenic fractions vary slightly according to the three reference elements (Fe, U and Nb) used in the calculations for the two groups of studied soils. The results also illustrated that most of the mercury content is of exogenic origin; therefore, total mercury variations are closely related to the content of exogenic mercury, while the lithogenic fraction exhibited no relationship with total mercury concentration. Moreover, application of the weathering indexes of Parker and the CaO/ZrO2 molar ratio supported the dependence of lithogenic mercury accumulation on weathering intensity in the studied calcareous soils. However, the significance of this relationship is stronger for more weathered calcareous soils; in such cases, fine-particle fractions are more developed, which encourages carrier phases such as organic materials and iron oxyhydroxides to become involved in more efficient fixation of mercury. Nevertheless, the formation of underlying layers of accumulated clay, i.e. argillic horizons, may restrain fixation of exogenic mercury by limiting its atmospheric input.

Impact of sedimentary processes and paleopedogenesis on Holocene Luvisol formation

stacking of periglacial layers: A differentiation of eluvial (E-) and illuvial (Bt-) horizon is already developed within the upper layer. The intermediate layer carries the main argillic horizon of those profi les whereas the within the upper layer. The intermediate layer carries the main argillic horizon of those profi les whereas the basal layer is only marginally affected by soil formation. By the help of soil micromorphology it was possible basal layer is only marginally affected by soil formation. By the help of soil micromorphology it was possible to identify numerous fragments of paleosol material within the intermediate layer (2Bt-horizon) accountto identify numerous fragments of paleosol material within the intermediate layer (2Bt-horizon) accounting for large proportions of the total clay content of this horizon. While the formation of the upper layer, ing for large proportions of the total clay content of this horizon. While the formation of the upper layer, parts of the intermediate layer were reworked and incorporated into the newly formed slope deposit. As a parts of the intermediate layer were reworked and incorporated into the newly formed slope deposit. As a result, the lower part of the upper and the whole intermediate layer contained large amounts of clay before result, the lower part of the upper and the whole intermediate layer contained large amounts of clay before the onset of Holocene pedogenesis. Recent lessivation, evidenced by undisturbed clay illuviations, affected the onset of Holocene pedogenesis. Recent lessivation, evidenced by undisturbed clay illuviations, affected the profi le. Consequently this soil formation masks prior differences in clay content due to included paleosol the profi le. Consequently this soil formation masks prior differences in clay content due to included paleosol material. Soil formation is dominated by the paleosol remnants and therefore elucidates the impact of late material. Soil formation is dominated by the paleosol remnants and therefore elucidates the impact of late glacial conditions on Holocene soils. glacial conditions on Holocene soils. Besides, a Luvisol was identifi ed which was not formed in periglacial slope deposits but in Holocene colBesides, a Luvisol was identifi ed which was not formed in periglacial slope deposits but in Holocene colluvium. In this case paleosol remnants were totally absent. Hence, a precise reconstruction of Luvisol-genesis luvium. In this case paleosol remnants were totally absent. Hence, a precise reconstruction of Luvisol-genesis is enormously improved by micromorphological analyses. is enormously improved by micromorphological analyses.

Sediment provenance and geomorphic development of soils in a blackwater ecosystem, South Carolina Coastal Plain

Mineral soil is a conundrum on southeastern U.S. blackwater floodplains because these freshwater ecosystems are known for slow-flowing streams bearing little suspended sediment. Investigations on soils along this riparian system revealed two distinct geomorphic surfaces, the modern swamp floodplain (classified as Inceptisols according to Soil Taxonomy) and slightly elevated landforms (intra-swamp terraces) with more developed soils (Alfisols and Ultisols). This study examined soil characteristics and sediment provenance on the Black River floodplain and its tributaries in the Atlantic Coastal Plain of South Carolina to determine the properties and pedogenic relationship between these two geomorphic surfaces and to propose a theory for the geomorphic evolution for soils on these landforms. Spatial characterization of the soils will benefit ecologists researching the biological aspects of blackwater ecosystems such as the concentration and flux of dissolved organic carbon (DOC). Results showed terrace soils had aquic moisture regimes while floodplain soils had peraquic moisture regimes. Floodplain surface horizons were organic carbon-rich (5% to 25% OC) but seldom with enough to qualify as organic soil material. Discontinuities occurred within the soils of both landforms indicating two distinct sedimentological environments. The fine-earth fraction of soil profiles on both landforms generally had upper strata composed mainly of silt and clay indicative of wash load sediments underlain with sandy strata indicative of bed load deposits. Fine clay distribution and fine clay:total clay ratios (FC/TC) showed argillic horizon development in the terrace subsoils but not in the floodplain soils. Micromorphology supported argillic horizons for the terraces, but also revealed modest clay accumulation in pores and channels of the floodplain soils. These floodplain clay features are interpreted to have formed during a period of subaerial weathering. The sandy strata were likely deposited during the beginning of the transgressions following the down cutting that occurred during the regressions and sea level lows. Silt fraction comparisons between the blackwater soils and soils on other landscapes in the region suggest the silts and clays likely were deposited in an estuarine environment late in the transgressions.

Soil genesis, optical dating, and geoarchaeological evaluation of two upland Alfisol pedons within the Tertiary Gulf Coastal Plain

Much of the Gulf Coastal Plain is mantled by sandy A and E soil horizons overlying finer-grained Bt horizons. Researchers have applied optical stimulated luminescence (OSL) dating to a variety of depositional settings, such as hillslopes and terraces, in an attempt to understand depositional versus pedogenic origins of the sandy horizons, and archaeological burial processes. These investigations have documented a range of integrity conditions from pristine to highly bioturbated. However, little work has been conducted in upland summits. Thus, we integrated field morphological descriptions, constituent mass balance reconstruction, and optical dating to reconstruct the timing and pedogenic pathways of two summit Alfisols on the Tertiary Gulf Coastal Plain in Texas. Investigations reveal that the sandy A and E horizons and the Bt horizons in each pedon are genetically related, with textural contrasts resulting from pedogenic processes. Optical dating revealed highly complex age structures strongly influenced by bioturbation, weathering, and the presence of coarse clay plus total silt particle-sizes. Pedogenic mixing is extensive in the A and E horizons, which effect apparent OSL ages <10,000years due to admixture of recently and partially bleached grains to the matrix. Decreased mixing occurs within the argillic horizon of each pedon, and ages increase systematically with depth. In all horizons pedogenic weathering and mixing have altered the 40K, U and Th content and environmental dose rates, with concomitant changes in OSL ages. Apparent maximum age calculations provide insight into the most probable oldest equivalent dose group and suggest that the investigated soils began to weather no later than 90–112ka, and 40–62ka, respectively, which greatly precedes human entry of into North America. High overdispersion of equivalent dose values in the sandy horizons reflects on-going pedoturbation, which varies between pedons and may result in differential archaeological preservation potential.

Extent of vegetation-free zone necessary for silvopasture establishment of eastern black walnut seedlings in tall fescue

Silvopasture—the integration of trees, forage, and livestock can be established by planting trees in existing pastures. Successful tree establishment and acceptable tree growth in existing tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] pastures requires a vegetation-free zone near the tree base. This study was conducted to determine how large a vegetation-free zone was necessary for the establishment of black walnut (Juglans nigra L.) in tall fescue pastures. Half-sib black walnut seeds were planted in seven different-sized vegetation-free zones [0.0 (control), 0.3, 0.6, 0.9, 1.2, 1.5, and 1.8 m radii] that were created and maintained by applying glyphosate. The study included two consecutive planting years at two locations, one in central Missouri and another in north-central Missouri. The central Missouri site was underlain with well drained, deep soil while the other site was underlain with a poorly drained soil with a defined argillic horizon. Tree height growth was greatest in 0.9-m or larger vegetation-free zones. Diameter growth was greatest in 1.2-m vegetation-free zones and larger. The results suggest that a minimum of a 1.2-m vegetation-free zone in tall fescue pastures should be used to maximize black walnut height and diameter growth in the critical first years of tree establishment.

Origin of glossic horizons in Cryalfs of the eastern Rocky Mountains, USA

Cryalfs are the predominant suborder along the eastern front of the Rocky Mountains from northern NM through MT and into Alberta. Approximately 50% of the Cryalfs in the western USA contain a glossic horizon, defined as a degraded argillic horizon containing properties of both an E and a Bt horizon. Using the NRCS database, we examined 257 Cryalf soil series, 79 of which contain a glossic horizon. The glossic horizon occurs at an average depth of 32cm and averages 24cm thick. The glossic horizon is most commonly an E/Bt with textures similar to the E above and Bt below. Waxy or glossy argillans are common, as well as clay-enriched nodules and seams. Laboratory data are available for only 10 Cryalf pedons containing a glossic horizon. Based on these data, the glossic horizon contains an average of 24% clay, 1.0 clay/CEC7, 0.6% organic C, a cation-exchange capacity of 19cmolc/kg soil, 85% base saturation, and a pH of 5.6. Several theories for the origin of the glossic horizon were considered from a weight-of-evidence approach. The glossic horizon in Cryalfs of the Rocky Mountains may be attributed to an input of eolian silt which creates a lithologic discontinuity and a mid-Holocene (5000yr BP to present) lowering of treeline containing the strongly podzolizing species Picea engelmannii and Abies lasiocarpa. Although glossic horizons are common in upper montane soils now containing lodgepole pine (Pinus contorta), they are uncommon in lower montane soils supporting lodgepole and ponderosa (Pinus ponderosa) pines.

Soil formation in loess-derived soils along a subhumid to humid climate gradient, Northeastern Iran

In order to contribute to the understanding of carbonate enrichment and clay illuviation in loess-derived soils of subhumid to humid regions, the development of soils was studied along a climate gradient with xeric and udic soil moisture regimes (SMR) and thermic and mesic soil temperature regimes (STR), respectively, in the Golestan Province, Northeastern Iran. Six representative pedons along a climate gradient were investigated. Soils were classified mainly as Hapludalfs and Haploxeralfs. Stability of the geomorphic surface under forest vegetation associated with high leaching conditions has provided appropriate conditions for decalcification followed by clay migration through the profile and formation of argillic horizons in all the studied soils. Clay content of the Bt horizons, soil organic carbon concentration of the A horizons, and depth of the Bk horizons increased significantly with increasing precipitation and decreasing temperature. There was a considerable decrease in silt content with soil development. The main pedofeatures observed in the Bt horizons were clay coatings and decalcified zones. Nodules, coatings and hypocoatings were the main calcitic pedofeatures observed in the Bk horizons. Occurrence and preservation of clay coatings were more pronounced in the udic regions with illite and vermiculite as the dominant clay minerals. Type of clay minerals, shrink/swell properties, and precipitation rate are factors affecting the abundance and preservation of clay coatings. In the strongly developed horizons of the udic SMR, the occurrence of vermiculite clay minerals could reduce the shrink/swell potential and increase the amount of clay coatings. The presence of crystallitic b-fabrics and the high carbonate contents (CaCO3) in the lower horizons (Bk) were mainly related to decalcification processes under descending water flow in the overlying horizons.

Characterization of seasonal freeze-thaw and potential impacts on soil erosion in northeast China

Zhao, Y., Wang, E., Cruse, R. M. and Chen, X. 2012. Characterization of seasonal freeze-thaw and potential impacts on soil erosion in northeast China. Can. J. Soil Sci. 92: 567–571. Freeze-thaw cycles are regarded as a critical factor inducing and accelerating gully erosion in the Black soil region (Chernozem) of northeast China. The major objective of this study was to identify the effect of seasonal freeze-thaw processes on soil structure relevant to soil erosion. Perched water due to an argillic horizon brings about higher water potential in the top soil, which lowers the soil shear strength and increases the risk of soil erosion by rainfall and surface flow; and the argillic horizon, with a higher clay content, is more vulnerable to freeze-thaw processes, which break or weaken the structure of the argillic horizon, increasing its vulnerability to gully erosion.

Biomantle Formation and Site Preservation on Terraces of Low Order Streams in the Ozark Uplands

Many terraces of low order streams in the Ozark uplands appear to have been stable since at least the early Holocene, indicated by strongly expressed soils with argillic horizons and early Holocene artifacts recovered from surface and shallow sub-surface contexts. These terraces hold sites that likely represent land use practices very different from those along better-studied large streams in the area. Artifact depth distribution curves show that a biomantle with accompanying stone zone has not formed under many of these terraces, despite their age. This contrasts markedly with much swifter rates of biomantle formation reported elsewhere. The lack of a fully formed biomantle in a soil of this age may be due to forces countervailing the downward movement of clasts through bioturbation, or slower rates of bioturbation overall.

구릉지 토양인 아산통의 분류 및 생성

Soil Taxonomy 분류체계 변화에 대응하여 구릉지에 널리 분포하는 토양으로 Inceptisols인 Typic Dystrudepts로 분류되고 있는 아산통을 재분류하고, 그 생성을 구명하기 위하여 아산통 대표단면의 형태적 특성을 조사하고, Soil Taxonomy의 표준 분석방법인 Soil survey laboratory methods manual에 따라서 토양을 분석하여 Laboratory data sheets를 작성하였다. A층 (0~18 cm)은 암황갈색 (10YR 4/4)의 자갈이 있는 양토이고, BA층 (18~30 cm)은 진갈색 (7.5YR 5/6)의 자갈이 있는 양토, Bt1층 (30~52 cm)은 적색 (2.5YR 4/6)의 자갈이 있는 식양토, Bt2층 (52~98 cm)은 적색 (2.5YR 4/8)의 자갈이 있는 식양토, C층 (98~160 cm)은 적색 (2.5YR 4/8)의 자갈이 있는 양토이다. 구릉지 잔적층을 모재로 하는 토양으로 주로 임지로 이용되고 있다. udic 토양수분상과 mesic 토양온도상을 보유하며, 배수 양호하다. 아산통은 0~18 cm 깊이에 ochric 감식표층을 보유하고, 30~98 cm 깊이에서 점토집적층인 argillic층을 보유하고 있다. 또한 argillic층 상부경계에서 125 cm 아래 깊이인 155 cm 깊이에서의 염기포화도 (양이온 합)가 7.8%로 35% 미만이다. 따라서 아산통은 Inceptisols이 아니라 Ultisols로 분류되어야 한다. 아산통은 udic 토양수분상을 보유하고 있으므로 Udults로 분류할 수 있으며, Hapludults의 분류기준을 충족시키고 있다. Typic Hapludults의 분류기준을 충족시키고 있으며, 토성속 제어부위에서의 토성속이 식양질이고, 토양온도상이 mesic 온도상이기 때문에 아산통은 Fine Loamy, mesic family of Typic Dystrudepts가 아니라 Fine loamy, mesic family of Typic Hapludults로 재분류되어야 한다. 아산통은 경사가 비교적 완만하여 지형이 안정되어 있는 구릉지에 분포하고 있으므로 침식이 일어나는 것에 비하여 토양수의 하향이동에 따른 점토집적작용과 염기용탈작용이 우선되고 있다. 그 결과 점토집적층인 argillic층을 보유하는 토양으로 생성 발달되었다. 또한 Alfisols과 Ultisols을 구분하는 가장 기본적인 분류기준인 기준깊이에서의 염기포화도 (양이온 합)가 35% 미만으로서 Alfisols이 아니라 강산성 토양인 Ultisols로 발달하였다. This study was conducted to reclassify Asan series based on the second edition of Soil Taxonomy and to discuss the formation of Asan series distributed on the rolling to hilly areas. Morphological properties of typifying pedon of Asan series were investigated and physico-chemical properties were analyzed according to Soil survey laboratory methods manual. The typifying pedon of Asan series has dark yellowish brown (10YR 4/4) gravelly loam Ap horizon (0-18 cm), strong brown (7.5YR 5/6) gravelly clay loam BA horizon (18-30 cm), red (2.5YR 4/6) gravelly clay loam Bt1 horizon (30-52 cm), red (2.5YR 4/8) gravelly clay loam Bt2 horizon (52-98 cm), and red (2.5YR 4/8) gravelly clay loam C horizon (98-160 cm). The typifying pedon has an argillic horizon from a depth of 30 to 98 cm and a base saturation (sum of cations) of less than 35% at 125 cm below the upper boundary of the argillic horizon. It can be classified as Ultisol, not as Inceptisol. It has udic soil moisture regime, and can be classified as Udult. Also that meets the requirements of Typic Hapludults. It has 18-35% clay at the particle-size control section, and has mesic soil temperature regime. Therefore Asan series can be classified as fine loamy, mesic family of Typic Hapludults, not as fine loamy, mesic family of Typic Dystrudepts. Asan series occur on rolling to hilly areas in residual materials derived from granite gneiss, schist, and gneiss rocks. They are developed as Ultisols with clay mineral weathering, translocation of clays to accumulate in an argillic horizon, and leaching of base-forming cations from the profile for relatively long periods under humid and temperate climates in Korea.

하성평탄지 토양인 청원통의 분류 및 생성

하성평탄지에 분포하는 토양으로 Inceptisols인 Fluvaqentic Epiaquepts로 분류되고 있는 청원통을 재분류하고, 그 생성을 구명하기 위하여 청원통 대표단면의 형태적 특성을 조사하고, Soil Taxonomy의 표준 분석방법인 Soil survey laboratory methods manual에 따라서 토양을 분석하여 Laboratory data sheets를 작성하였다. Ap층 (0~18 cm)은 암회갈색 (2.5Y 4/2)의 미사질양토이고, BA층 (18~30 cm)은 암회갈색 (2.5Y 4/2)의 미사질양토, Bt1층 (30~60 cm)은 암황갈색 (10YR 4/6)의 미사질양토, Bt2층 (60-91 cm)은 진갈색 (7.5YR 4/6)의 미사질식양토, BC층 (91~104 cm)은 갈색 (10YR 4/4)의 미사질양토, C층 (104~160 cm)은 잡색 (7.5YR 4/6, 7.5YR 5/2)의 미사질양토이다. 하성평탄지 충적층을 모재로 하는 토양으로 주로 논으로 이용되고 있다. udic 토양수분상과 mesic 토양온도상을 보유하며, 배수 약간양호하다. 청원통은 0~18 cm 깊이에서 ochric 감식표층을 보유하고, 30~91 cm 깊이에서 점토집적층인 argillic층을 보유하고 있다. 또한 argillic층의 상부경계에서 125 cm 아래 깊이인 155 cm 깊이에서의 염기포화도 (양이온 합)가 63.9%로 35% 이상이다. 따라서 청원통은 Inceptisols이 아니라 Alfisols로 분류되어야 한다. 청원통은 토양표면에서 50 cm 이내 깊이의 1개 이상의 층위에서 aquic 조건을 보유하고, 25~40 cm 깊이의 모든 층위에서 산화환원성인을 보유하고 있으나, argillic층의 상부 12.5 cm 깊이에서는 이러한 조건을 충족시키지 못하고 있으므로 Aqualfs가 아니라 Udalfs 아목으로 분류할 수 있다. natric층, glossic층, fragipan 등을 보유하지 않으며 Hapludalfs의 분류기준을 충족시키고 있다. 논토양으로 토양 표면에서 30 cm 깊이까지만 회색화 되어 있는 anthraquic 조건을 보유하고 있으므로 아군은 Anthraquic Hapludalfs의 분류할 수 있다. 토성속 제어부위에서의 토성속이 미사식양질이고, 토양온도상이 mesic 온도상이기 때문에 청원통은 Fine silty, mixed, nonacid, mesic family of Fluvaquentic Epiaquepts가 아니라 Fine silty, mixed, mesic family of Aeric Epiaqualfs로 분류되어야 한다. 청원통이 제4기 신층인 충적세 (Holocene)의 퇴적물에 의하여 형성된 하성충적층을 모재로 하고 있으면서도 점토집적층인 argillic층을 보유하는 토양으로 생성 발달한 것은 과거 어느 시기에 충적이 일어난 후 비교적 오랫동안 새로운 충적물이 별로 퇴적되지 않은 비교적 안정한 지형에 분포하고 있기 때문이라고 생각된다. 특히 벼 재배기간 동안 담수되어 있기 때문에 점토의 이동과 집적이 빠른 속도로 일어나 토양 발달이 빠른 속도로 진행되었을 뿐만 아니라 Ca, Mg, K, Na 등의 염기의 하향 이동도 계속적으로 일어나 argillic층 상부경계에서 125 cm 아래 깊이까지도 이들 염기성분이 집적되고 있을 것이다. 따라서 청원통이 Inceptisols이 아니라 Alfisols로 생성 발달한 것이라고 생각된다. This study was conducted to reclassify Cheongweon series based on the second edition of Soil Taxonomy and to discuss the formation of Cheongweon series distributed on broad continental alluvial plains. Morphological properties of typifying pedon of Cheongweon series were investigated and physico-chemical properties were analyzed according to Soil survey laboratory methods manual. The typifying pedon of Cheongweon series has dark grayish brown (2.5Y 4/2) silt loam Ap horizon (0~18 cm), dark grayish brown (2.5Y 4/2) silt loam BA horizon (18~30 cm), dark yellowish brown (10YR 4/6) silty clay loam Bt1 horizon (30~60 cm), strong brown (7.5YR 4/6) silty clay loam Bt2 horizon (60~91 cm), brown (10YR 4/4) silt loam BC horizon (91~104 cm), and mottled (7.5YR 4/6, and 7.5YR 5/2) silt loam C horizon (104~160 cm). The typifying pedon has an argillic horizon from a depth of 30 to 91 cm and a base saturation (sum of cations) of 35% or more at 125 cm below the upper boundary of the argillic horizon. It can be classified as Alfisol, not as Incceptisol. It has udic soil moisture regime, and can be classified as Udalf. Also that meets the requirements of Hapluadalf. It has anthraquic condition, and keys out as Anthraquic Hapludalf. That has fine silty textural family, and has mesic soil temperature regime. Therefore Cheongweon series can be classified as fine silty, mixed, mesic family of Anthraquic Hapludalfs, not as fine silty, mixed, mesic family of Fluvaquentic Epiaquepts.

Pedogenetic investigation of soil degradation on a deforested loess hillslope of Golestan Province, Northern Iran

Genesis, mineralogy, and micromorphology of soils formed on a forest and adjacent cultivated loess hillslope were investigated to assess the effects of deforestation and hillslope position on soil properties and the intensity of soil degradation. The study revealed that deforestation caused a loss of soil organic carbon, a reduction of cation exchange capacity, and an increase in carbonates in the surface soil. The soils of the different slope positions of the forest land were Alfisols and Mollisols with well-developed argillic horizons. Speckled b-fabric of the argillic horizons and the crystallitic b-fabric of the underlying calcic horizon are evidence for a more stable landscape under forest ecosystem. Downward leaching caused decalcification of the upper horizons and clay movement in the profile. Formation of the mollic epipedon in the forest land confirms the accumulation of organic carbon and lower erosion in the surface soil. Soils of the adjacent cultivated area however, are less-developed, and classified as Inceptisols and Mollisols. Absence of the mollic epipedon in the shoulder, backslope and footslope positions, presence of the near surface calcic horizon and absence of argillic horizon in all slope positions are due to severe erosion. Absence of speckled b-fabric in all the slope positions of the deforested land is evidence that downward and surface movements of water have resulted in soil erosion and flooding. Higher smectite concentrations and occurrence of vermiculite in the forest area indicate favorable moisture availability. Pedology is an effective way of documenting the adverse effects of land use change especially in the hilly regions.

The impact of biotic/abiotic interfaces in mineral nutrient cycling: A study of soils of the Santa Cruz chronosequence, California

Abstract Biotic/abiotic interactions between soil mineral nutrients and annual grassland vegetation are characterized for five soils in a marine terrace chronosequence near Santa Cruz, California. A Mediterranean climate, with wet winters and dry summers, controls the annual cycle of plant growth and litter decomposition, resulting in net above-ground productivities of 280–600 g m−2 yr−1. The biotic/abiotic (A/B) interface separates seasonally reversible nutrient gradients, reflecting biological cycling in the shallower soils, from downward chemical weathering gradients in the deeper soils. The A/B interface is pedologically defined by argillic clay horizons centered at soil depths of about one meter which intensify with soil age. Below these horizons, elevated solute Na/Ca, Mg/Ca and Sr/Ca ratios reflect plagioclase and smectite weathering along pore water flow paths. Above the A/B interface, lower cation ratios denote temporal variability due to seasonal plant nutrient uptake and litter leaching. Potassium and Ca exhibit no seasonal variability beneath the A/B interface, indicating closed nutrient cycling within the root zone, whereas Mg variability below the A/B interface denotes downward leakage resulting from higher inputs of marine aerosols and lower plant nutrient requirements. The fraction of a mineral nutrient annually cycled through the plants, compared to that lost from pore water discharge, is defined their respective fluxes Fj,plants = qj,plants/(qj,plants + qj,discharge) with average values for K and Ca (FK,plants = 0.99; FCa,plants = 0.93) much higher than for Mg and Na (FMg,plants 0.64; FNa,plants = 0.28). The discrimination against Rb and Sr by plants is described by fractionation factors (KSr/Ca = 0.86; KRb/K = 0.83) which are used in Rayleigh fractionation-mixing calculations to fit seasonal patterns in solute K and Ca cycling. KRb/K and K 24 Mg / 22 Mg values (derived from isotope data in the literature) fall within fractionation envelopes bounded by inputs from rainfall and mineral weathering. KSr/Ca and K 44 Ca / 40 Ca fractionation factors fall outside these envelopes indicating that Ca nutrient cycling is closed to these external inputs. Small net positive K and Ca fluxes (6–14 mol m−2 yr−1), based on annual mass balances, indicate that the soils are accumulating mineral nutrients, probably as a result of long-term environmental disequilibrium.

Morphological, chemical and mineralogical characterization of developing soils and their management in the western Siwalik Himalayas

The western Siwalik Himalayas of India experienced the last climate shift 3500 years ago and the soils have been marked by rigorous human activities for a few centuries. An attempt was made to investigate the interactions between soil-forming factors and processes in soil development in relation to land forms and climate change. The hallmark of the soils is the considerable heterogeneity in solum and regolith thickness, horizon boundaries, structural development in surface soils, pH, electrical conductivity and soil mineralogy, irrespective of landscape form and position. A remarkable feature of the soils is the development of deep argillic horizons, or B horizons, in certain landscape positions. The minerals identified were quartz, micas and feldspars in the sand and silt fractions. Illite, kaolinite, vermiculite, smectite and chlorite were present in the clay fractions. Soils under forest vegetation and those recently brought under cultivation belong to Typic Hapludalfs. Soils cultivated over centuries, however, failed to qualify as Alfisols and were classified as Typic/Dystric Eutrudepts. The eroded barren soils were similarly classified as Typic Udorthents. All the soils were low to medium in available nitrogen and phosphorus. The use of nitrogen and phosphorus fertilizer is therefore needed to ameliorate nutrient deficiency and boost crop production. Because of the presence of appreciable amounts of potassium-bearing minerals, soils are likely to be non-responsive to potassium application. The soils of the Dala series (Typic Hapludalfs) are located on moderate hill slopes and thus soil erosion is less severe than for the Mansu series (Typic Udorthent). In the Chamror and Dhar series (Typic/Dystric Eutrudepts) soil erosion is not a serious problem because of terracing and the finer texture of the soils. Crops can thus be grown on profile-stored moisture during dry periods and limited grazing may be permitted.