ABSTRACT Currently in Brazil, large grain cultivation projects on Plinthosols are a reality, however, there is little or no knowledge of the real mechanism of formation of the plinthite feature, in addition to what is reported in the literature as being a product of oxidation-reduction processes of iron element. This study evaluates iron redoximorphic features and investigates their chemical and mineralogical composition in two profiles of Plinthosols from the Araguaia River plain (P1 and P2). The study strengthens the understanding of the pedogenetic processes involved in the formation of mottles and plinthite. In this sense, it assesses whether the formation mechanisms corroborate the literature. Soil features were sampled in the upper right and left position at the initial plinthic horizon, upper right and left position at the main plinthic horizon, and lower right position at the base horizon of the plinthite zone in the profile. Separated samples comprising the soil matrix, mottles, and plinthite under natural moisture conditions were ground into powder form for chemical determinations by X-ray fluorescence (XRF), sulfuric acid attack (H2SO4), sodium dithionite-citrate-bicarbonate (DCB), and ammonium acid oxalate; and mineralogical determinations by X-ray diffraction. Iron contents in all determined forms were always higher in the plinthite feature, intermediate in the mottle feature, and lower in the soil matrix feature. Most of the Fe in all redoximorphic features is included in the structure of primary minerals and their derivatives (vermiculite, illite, and VHEs). Only part of the iron present (about 35.40 % in P1 and 41.98 % in P2) is detected in the form of oxides such as goethite and hematite, which could be formed in redox processes. The mottle and plinthite features under study are not the product of the classic process of segregation, mobilization, and accumulation of iron as a consequence of redox processes. These features were formed or emerged as a result of a relatively slow and constant weathering process of their source material, which is gradually decomposed in an aqueous medium, releasing most of its components. These components include iron and more mobile elements such as bases and silicon, which leave the system through drainage water, and of which a small part may eventually recombine to form new less complex minerals such as kaolinite and oxides. Brazil reality however feature oxidationreduction oxidation reduction element P (P P2. P2 . sense profile Xray X ray XRF, XRF , (XRF) H2SO4, H2SO4 HSO H SO (H2SO4) dithionitecitratebicarbonate dithionite citrate bicarbonate DCB, DCB (DCB) oxalate diffraction vermiculite, vermiculite (vermiculite illite VHEs. VHEs VHEs) about 3540 35 40 35.4 4198 41 98 41.9 hematite segregation mobilization material medium silicon water (XRF H2SO (H2SO4 (DCB 354 3 4 35. 419 9 41. (H2SO

ABSTRACT The term toposequence, proposed to designate a lateral succession of soils on a slope due to the influence of topography, began to be used differently over time, distancing itself from its original concept. Here, we discuss how this concept has been used since its inception. We carried out bibliometric analyses of publications in the database available on the Web of Science since 1900. Three main approaches and related concepts, explicit or not, one at a regional scale and two others at a local scale were identified. From this analysis, we suggest: a) when the approach is regional, the term geomorphic surface or position in the landscape should be used to address the spatial distribution and genetic implications of soils at this scale; b) when dealing with series/sequences of soils on slopes for mapping purposes or discontinuous profiles that emphasize taxonomic classification, the term catena should be used; c) when the determining factor of the soil sequence is climatic, biotic, lithological, chronological, the corresponding term climo-, bio-, litho- or chronosequence should be used; d) when dealing with a lateral succession of horizons in the continuum on slopes, resulting from the influence of topography on soil formation, which may reflect the soil contribution to the model evolution, only in this case should the term toposequence be used, returning to its original concept. time Here inception 1900 concepts not identified analysis suggest b seriessequences series sequences classification c climatic biotic lithological chronological climo, climo , climo- bio, bio bio- litho d formation evolution 190 19 1

RESUMO O oxyfluorfen é um herbicida pré-emergente aplicado via solo; porém, os atributos do solo não vêm sendo considerados na determinação das doses do produto. Objetivou-se avaliar a biodisponibilidade do herbicida oxyfluorfen em solos do Cerrado com atributos contrastantes. O experimento foi desenvolvido em esquema fatorial 6 x 8, com 6 repetições. Os fatores avaliados foram tipos de solo [Gleissolo Melânico distrófico (GMd), Latossolo Vermelho ácrico (LVw), Latossolo Vermelho distrófico (LVd), Neossolo Quartzarênico órtico (RQo), Neossolo Flúvico Tb distrófico (RYbd) e areia lavada] e doses de oxyfluorfen (0; 360; 480; 720; 1.440; 2.880; 4.320; e 5.760 g i.a. ha-1). A biodisponibilidade do herbicida foi determinada pela metodologia do bioensaio. A dose que garantiu 80 % de controle de Cucumis sativum (C80%) variou de 9,9 (LVw) a 1.884,4 g i.a. ha-1 (GMd), o que pode ser atribuído à elevada capacidade de retenção do herbicida no GMd, conforme verificado pela relação adsortiva. A textura do solo não apresentou correlação com a biodisponibilidade de oxyfluorfen. No LVd, solo da mesma classe e com textura semelhante (argilosa) à do LVw, a CR80% foi 76 vezes maior (754,28 g i.a. ha-1). Além disso, no RYbd, que apresenta textura arenosa, a C80% foi ainda maior (1.256,9 g i.a. ha-1). A capacidade de troca catiônica (CTC) (-0,83**) foi o único atributo do solo capaz de predizer a biodisponibilidade do herbicida. A biodisponibilidade do oxyfluorfen é altamente dependente dos atributos do solo e, em solos do Cerrado, pode ser predita pela CTC. préemergente pré emergente porém produto Objetivouse Objetivou se contrastantes 8 repetições Gleissolo GMd , (GMd) LVw LVd (LVd) RQo, RQo (RQo) RYbd (RYbd lavada 0 (0 360 480 720 1.440 1440 1 440 2.880 2880 2 880 4.320 4320 4 320 5760 5 760 5.76 ia i i.a ha1. ha1 ha . ha-1) bioensaio C80 C (C80% 99 9 9, (LVw 18844 884 1.884, ha- adsortiva argilosa (argilosa CR80 CR 7 754,28 75428 754 28 (754,2 disso arenosa 1.256,9 12569 256 (1.256, CTC (CTC 0,83** 083 83 (-0,83** (GMd (LVd (RQo ( 36 48 72 1.44 144 44 2.88 288 88 4.32 432 32 576 5.7 C8 (C80 1884 1.884 CR8 754,2 7542 75 (754, 1.256, 1256 25 (1.256 0,83* 08 (-0,83* 3 1.4 14 2.8 4.3 43 57 5. (C8 188 1.88 754, (754 1.256 125 (1.25 0,83 (-0,83 1. 2. 4. (C 18 1.8 (75 1.25 12 (1.2 0,8 (-0,8 (7 1.2 (1. 0, (-0, (1 (-0 (-

ABSTRACT Oxyfluorfen is a pre-emergent herbicide applied via soil; however, the soil attributes have not been considered to predict the herbicide doses. This study aimed to evaluate the bioavailability of the oxyfluorfen herbicide in Brazilian Savanna soils with contrasting attributes. The experiment was carried out in a 6 x 8 factorial scheme, with 6 replications. The evaluated factors were soil types [Gleissolo Melânico distrófico - GMd (Typic Humaquept); Latossolo Vermelho ácrico - LVw (Rhodic Acrustox); Latossolo Vermelho distrófico - LVd (Rhodic Haplustox); Neossolo Quartzarênico órtico - RQo (Typic Quartzpsamment); Neossolo Flúvico Tb distrófico - RYbd (Fluventic Dystrustept); and washed sand] and oxyfluorfen doses (0; 360; 480; 720; 1,440; 2,880; 4,320; and 5,760 g a.i. ha-1). The herbicide bioavailability was determined according to the bioassay methodology. The dose that provided 80 % of Cucumis sativum control (C80%) ranged from 9.9 (LVw) to 1,884.4 g a.i. ha-1 (GMd), what can be attributed to the high sorption of the herbicide in the GMd, as observed by the adsorptive rate. The soil texture did not show correlation with the oxyfluorfen bioavailability. In the LVd, which is from the same order and with texture similar to that of the LVw, the C80% was 76 times higher (754.28 g a.i. ha-1). Furthermore, for the RYbd, which is a sandy soil, the C80% was even high (1,256.9 g a.i. ha-1). The cation exchange capacity (CEC) (-0.83**) was the only soil attribute able to predict the herbicide bioavailability. The oxyfluorfen bioavailability is highly dependent on the soil attributes, and, in Brazilian Savanna soils, it can be predicted using the CEC. preemergent pre emergent however scheme replications Gleissolo Typic Humaquept Humaquept) Rhodic Acrustox Acrustox) Haplustox Haplustox) Quartzpsamment Quartzpsamment) Fluventic Dystrustept Dystrustept) sand 0 (0 360 480 720 1,440 1440 1 440 2,880 2880 2 880 4,320 4320 4 320 5760 5 760 5,76 ai i a.i ha1. ha1 ha . ha-1) methodology C80 C (C80% 99 9 9. (LVw 18844 884 1,884. ha- , (GMd) rate 7 754.28 75428 754 28 (754.2 Furthermore 1,256.9 12569 256 (1,256. CEC (CEC 0.83** 083 83 (-0.83** ( 36 48 72 1,44 144 44 2,88 288 88 4,32 432 32 576 5,7 C8 (C80 1884 1,884 (GMd 754.2 7542 75 (754. 1,256. 1256 25 (1,256 0.83* 08 (-0.83* 3 1,4 14 2,8 4,3 43 57 5, (C8 188 1,88 754. (754 1,256 125 (1,25 0.83 (-0.83 1, 2, 4, (C 18 1,8 (75 1,25 12 (1,2 0.8 (-0.8 (7 1,2 (1, 0. (-0. (1 (-0 (-

ABSTRACT. Phosphorus (P) is one of the most important elements used in fertilizing soils in tropical regions due to the low efficiency of phosphate fertilization. This work aimed to fractionate inorganic P (Pi) in tropical soils of different mineralogical compositions and to relate these fractions with their respective phosphate buffer capacity (PBC) indicators. The soils were characterized physically, chemically and mineralogically. Additionally, we evaluated the P concentration that remained in solution of soil after equilibrium was met; this was termed P remaining (P-rem). In general, the Pi fractions of soils did not correlate with the PBC indicators. The P-H2O fraction showed a negative correlation with the P-Al fraction. Ferric minerals did not influence P fixation. P-rem showed a strong correlation with the maximum P adsorption capacity, adsorption energy, and the amorphous and crystalline forms of Fe. The minerals of aluminum contributed the most to P fixation. P-rem was the best estimator of PBC. The soils with high, moderate and low rates of P fixation showed high amounts of the fractions P-Al, P-Ca, and P-Fe, respectively. The results showed that P fixation was influenced by the fractions of P in the soil, suggesting that the efficiency of phosphate fertilizers in tropical soils depends on the mineralogy of the clay fraction within those soils.

RESUMO O fósforo (P) é um dos nutrientes que mais limita a produtividade agrícola, principalmente em solos tropicais. Biocarvão enriquecido tem sido proposto com o intuito de incrementar a biodisponibilidade de P e de outros nutrientes no solo. Assim, objetivou-se avaliar a disponibilidade do fósforo em biocarvão fosfatado (composto de biomassa e solo) em função da mistura de superfosfato triplo antes e após o processo de pirólise. Produzimos oito tipos de biocarvão enriquecido via pirólise, combinando solo arenoso ou argiloso com casca de arroz ou de café, e adicionando superfosfato triplo antes ou depois da pirólise. O aquecimento do fertilizante fosfatado durante o processo de pirólise resultou em maior cristalinidade dos fosfatos, menor teor de frações lábeis de P e menor teor de P disponível nos biocarvões fosfatados do que quando o superfosfato foi adicionado após a pirólise.

ABSTRACT Phosphorus (P) is one of the nutrients that most limits agricultural productivity, especially in tropical soils. Enriched biochar has been proposed to increase the bioavailability of P and other nutrients in the soil. Thus, the objective of this study was to evaluate the availability of P in phosphate biochar (composed of biomass and soil) as a function of the triple superphosphate mixture before and after the pyrolysis process. We produced eight types of enriched biochar via pyrolysis by combining sandy or clayey soil with rice or coffee husk, and by adding triple superphosphate before or after pyrolysis. The heating of the phosphate fertilizer during the pyrolysis process resulted in a higher crystallinity of the phosphates, lower content of labile fractions of P and lower content of available P in phosphate biochars than when the superphosphate was added after pyrolysis.

RESUMO Pequenas variações de relevo influenciam na drenagem e no escoamento superficial, contribuindo para a formação de horizontes superficiais arenosos e subsuperficiais endurecidos (fragipãs e, ou, duripãs) em solos dos Tabuleiros Costeiros. Este trabalho investigou a pedogênese em área de Tabuleiros Costeiros com baixa amplitude altimétrica no Estado da Paraíba; secundariamente, buscamos contribuir para o aprimoramento do Sistema Brasileiro de Classificação de Solos (SiBCS). Quatro perfis de solos foram descritos e coletados para a realização das análises físicas e químicas de rotina, extrações de Fe, Si e Al por digestão sulfúrica, por ditionito-citrato-bicarbonato de sódio, por oxalato ácido de amônio e por pirofosfato de sódio, e as análises mineralógicas das frações areia e argila por difratometria de raios X. A densidade ótica do extrato de oxalato (ODOE) também foi determinada; os resultados obtidos foram estatisticamente avaliados utilizando o programa R. As variações do microrrelevo condicionando fluxos diferenciados de água, juntamente com a textura arenosa dos horizontes superficiais (A e E) e a menor relação areia grossa/areia fina no horizonte subsuperficial, parece favorecer o acúmulo de argila em profundidade nos Espodossolos desenvolvidos no ambiente dos Tabuleiros Costeiros. Para esses solos, o caráter argissólico em nível de subgrupo do SiBCS deveria ser incorporado. Além disso, fases mineralógicas amorfas e, ou, de baixa cristalinidade de Al têm importante participação na formação de horizontes fortemente cimentados (duripãs) dos Espodossolos. Finalmente, a ODOE mostrou-se eficiente como indicador de solos sob processo de podzolização e poderia ser utilizada como critério taxonômico para classificação de Espodossolos pelo SiBCS.

ABSTRACT Small variations of relief may change drainage and runoff and hence promote the formation of sandy surface horizons and hardened subsurface horizons (fragipans and/or duripans) in Coastal Tablelands soils. This study aimed to investigate the pedogenesis on Coastal Tablelands area with low range altimetry in Paraíba state; secondly, we also sought to contribute to the improvement of the Brazilian Soil Classification System (BSCS). Four soil profiles ware described and collected to be submitted to routine physical and chemical analysis, determination of Fe, Al and Si extracted by sulfuric acid digestion, sodium citrate-bicarbonate-dithionite and acid ammonium oxalate, sodium pyrophosphate, and mineralogical analysis in the sand and clay fractions by X-ray diffractometry. Optical density of the oxalate extract (ODOE) was also determined; the results were statistically evaluated using the R software. Microrelief variations conditioning differentiated water flows, along with the sandy texture of the surface horizons (A and E) and the lower coarse sand/fine sand ratio in the subsurface horizon, seem to promote clay accumulation in depth in the Spodosols developed on Coastal Tablelands environments. For this soils, the argilluvic (argissólico) character at the subgroup level of the BSCS should be incorporated. In addition, Al amorphous mineral phases and/or poorly crystalline play an important role in the formation of strongly cemented horizons (duripans) of the Spodosols, as also reported by other authors. Finally, the ODOE showed to be an efficient indicator of soils under podzolization process, being possible its use as a taxonomic criterion for classification of Spodosols by the BSCS.

ABSTRACT. We studied the mineralogical properties and chemical composition of different granites using energy dispersive X-ray spectroscopy coupled with scanning electron microscopy to understand the relationship between granite signatures and soil characteristics, including weathering patterns and soil fertility status. The discriminant analysis (DA) was based on soil physical and chemical properties and was used to differentiate soils developed from I- and S-type granites across contrasting climatic conditions in northeast Brazil. The DA identified the highest values of organic carbon, clay and plant nutrients as key variables to recognize soil profiles derived from I-type granites. In contrast, the greater sand contents and Al saturation distinguished soils developed from S-type granites. These results were related to the mineralogical characteristics of each granite type, such as a high percentage of silica-bearing minerals in the S-type granites. The highest concentrations of K, Ca, Mg, and P in I-type granites were found in feldspars, amphiboles, and apatite. These elements account for the majority of nutrients derived in their soil profiles. However, it seems that the harsh conditions of the humid tropical environment equalized the effect of the rocks on weathering rates-the difference in chemical index of alteration is more extreme in the dry region.

ABSTRACT Sequences of thick and eroded soils in hills surfaces are cultivated with banana since the beginning of the last century in the Northeast of Pernambuco (PE), Brazil. Measurements of soil properties depending on soil slope under intensive agricultural cultivation are limited mostly as the pedogenetic approach. This study aimed to identify the dominant soil types, to evaluate morphological, physical, chemical, and mineralogical properties of soil profiles, and link them to the relief position under continuous banana cropping, in the transition Mata-Agreste of PE. Three slope classes and soil profiles were considered: Profile 1 (P1), upper third of the elevation slope; Profile 2 (P2), middle third of the slope; and Profile 3 (P3) lower third. They were opened, described, and soil samples collected from all horizons at a typical slope of the region. Independent of relief position and land use, all soils are deep (>1.50 m) and present the argic horizons (Bt) developed in all steeply sloping surfaces (15-33 %). The Bt horizon presented the highest values of soil bulk density and microporosity. Despite the presence of illite, all the soil profiles showed remarkable degree weathering, are mostly kaolinitic, besides presenting goethite and quartz in the soil clay fraction, and predominance of quartz in the silt and sand fraction. Water-stable aggregates >2 mm were dominant in all the relief positions. Acidity, low cation exchange capacity, and in general, nutrient poverty were observed in the soil profiles, as opposed accumulation of exchangeable cations on the lower third of the slope (P3). However, the soil properties were affected by land use and water erosion. The Ap horizons showed the highest values of pH, exchangeable bases, phosphorus available, and organic carbon due to agricultural practices, while the steepest slope (P2) had the lowest content of clay, phosphorus and mean weight diameter of aggregates, and higher organic carbon content, in the superficial horizon, due to removal and deposition by water erosion. From the upper third to the lower third of the slope, Nitic Acrisol, Haplic Acrisol, and Nitic Lixisol were formed.

ABSTRACT On the southern coast of Pernambuco State (PE), Brazil, lithotypes of the Cabo Basin (volcanic and sedimentary rocks), in association with the relief, allow the determination of the dynamics of the formation of Nitossolos Háplicos (Nitisols), including those with high levels of exchangeable aluminum. The objective of this study was to evaluate the influence of lithological diversity (basalt and sedimentary siliciclastic rocks) on the morphological, physical, chemical, and mineralogical properties of Nitossolos Háplicos along a slope (P1-summit, P2-backslope, P3-footslope) on the southern coast of PE, in order to consider its genesis and the relation of soil properties to adjacent environments and to evaluate its framing within the Brazilian Soil Classification System (SiBCS). The interaction of lithology/soil permeability and climate indicate significant differences in the mineralogical composition and dynamics of soil chemical elements. The profiles P1 and P2 are subject to monosialitization, ferralitization, and alitization processes. All profiles showed high Fe contents (ferric soils) and clay fractions, consisting primarily of kaolinite, goethite, hematite, and gibbsite, as well as quartz and feldspar in the sand and silt fractions. However, smectite minerals (P3) are probably inherited from the sedimentary source material. In the conglomerate samples, under P3, biotite, muscovite, and plagioclase were identified. Allytic characteristics (P3) are probably associated with the weathering of aluminous smectite minerals. These properties distinguish these soils from adjacent Nitossolos and other Nitossolos in Brazil. For the classification of soils according to SiBCS, considering the high levels of Fe and Al, Nitossolo Háplico distroférrico (P1 and P2) and Nitossolo Háplico alitiférrico (P3) are suggested, and according to the World Reference Base of Soils (WRB), the soils are classified as Ferritic Nitisols.

RESUMO A expansão da fronteira agrícola em diferentes ambientes geológicos no oeste do Estado do Pará, norte do Brasil, torna necessário conhecer a influência do material de origem sobre os atributos dos solos locais. Este estudo teve como objetivo avaliar a influência de diferentes materiais de origem sobre cinco perfis de solo ao longo de uma litosequência exposta pela rodovia BR-163, que vai de norte a sul pelo oeste do Pará. Os solos foram classificados, morfologicamente descritos e seus principais horizontes amostrados para análises físicas, mineralógicas e químicas, incluindo a determinação de micronutrientes, formas de fósforo e formas secundárias de ferro. Análises multivariadas foram usadas para agrupar as diferentes associações solo-material de origem. Os resultados demonstraram que a diversidade do material de origem foi determinante para os atributos do solo, sendo um fator condicionante para a formação de diferentes argilominerais. A análise multivariada agrupou os solos ao longo da litosequência em um grupo formado por perfis derivados de rochas ígneas básicas e intermediárias, e um segundo grupo constituído por perfis derivados de sedimentos e rochas sedimentares. O perfil derivado de rocha ígnea ácida apresentou maior similaridade com os perfis derivados de materiais sedimentares em comparação àqueles derivados de outras rochas ígneas.

ABSTRACT The expansion of the agricultural frontier into different geological environments in the west of the state of Pará, northern Brazil, makes it necessary to know the influence of the parent material on local soil attributes. This study aimed to evaluate the influence of different parent materials on five soil profiles along a lithosequence exposed by the BR-163 highway, which runs from north to south through western Pará. The soils were classified, morphologically described and their main horizons sampled for physical, mineralogical and chemical analyses, including the determination of micronutrients, forms of phosphorus and secondary forms of iron. Multivariate analysis was used to group the different soil-parent material associations. The results demonstrated that the diversity of the parent material was a determinant of soil attributes, and was a conditioning factor for the formation of different clay minerals. Multivariate analysis grouped the soils along the lithosequence into a group formed by profiles derived from basic and intermediate igneous rocks, and a second group consisting of profiles derived from sediments and sedimentary rocks. The profile derived from acidic igneous rock showed greater similarity with the profiles derived from sedimentary materials in comparison to those derived from other igneous rocks.

RESUMO Os Nitossolos dão suporte ao desenvolvimento agrícola e socioeconômico de muitos países subdesenvolvidos do mundo, incluindo o Brasil. Os Nitossolos brasileiros estão geralmente associados às rochas basálticas das regiões Sul e Sudeste. Entretanto, Nitossolos derivado de basalto também ocorrem na costa sul de Pernambuco, uma região em pleno desenvolvimento urbano, agrícola e industrial. Objetivando compreender as relações entre o clima e os atributos dos Nitossolos da costa sul de Pernambuco, foram realizadas descrições morfológicas, análises físicas e químicas, extrações seletivas de ferro e a determinação da mineralogia das frações areia, silte e argila de três perfis derivados de basalto ao longo de uma vertente. Os resultados demonstram que o clima da região implica em forte intemperização dos perfis, em grande perda de bases e favorece o processo de xantização, resultando na singular gênese de Nitossolos com matizes amarelados e caráter ácrico, fato que até o momento ainda não foi catalogado para esta ordem no sistema taxonômico brasileiro. Os resultados também demonstram a variação dos atributos físicos dos Nitossolos ao longo da vertente.

ABSTRACT Nitisols are livelihood sources of agricultural and socio-economic development in several underdeveloped countries worldwide, including Brazil. Brazilian Nitisols are usually associated with basaltic rocks found in the Southern and Southeastern regions of the country. However, Nitisols derived from basalt also occur on the southern coast of Pernambuco state, a region under full urban, agricultural, and industrial development. Aiming to understand the relationship between climate and attributes of Nitisols from the southern coast of Pernambuco, we performed morphological descriptions, physical and chemical analyzes, iron selective extraction, and soil mineralogy (sand, silt, and clay) for three basaltic soil profiles along a land slope. The results suggest a strong weathering of the profiles due to climate conditions, besides a great loss of basic cations and xanthization process, resulting in the natural genesis of acric Nitisols with yellowish coloration, which has not been yet cataloged for this soil order in the Brazilian taxonomic system. In addition, there is a variation for physical attributes of Nitisols along the slope.

ABSTRACT Archaeological Dark Earth (ADE) pedogenesis and pre-Columbian history are fundamental for understanding the biodiversity and pedodiversity of the Neotropical rainforest in the Amazon region. This study aimed to evaluate the morphological, physical, chemical, and mineralogical properties as well as NaOH-extractable organic matter [OM(NaOH)] in ADE and Mulatto Earth (ME) overlying volcanic rocks along a toposequence (four soil profiles) in western Amazonia, Brazil. The soil profiles show anthropic A horizons over an argic horizon (Bt) in the ADE (Humic, Pretic Luvisols) and Bi in the ME (Clayic, Dystric Cambisols). The soil-forming processes in all of the profiles are associated with organic matter accumulation, such as humification and melanization, besides the formation of organometallic complexes. Calcium, Mg, P, and organic carbon contents were higher in ADE compared to ME. High-activity clays are derived from parent volcanic material, distinguishing the soils studied from Amazonian soils (Tertiary Plateau, Terra Firme) and most Amazonian anthropic soils. The anthropic horizons generally have a large contribution from OM(NaOH), predominantly humin and humic acids associated with Ca, Mg, and poorly crystalline Al hydroxides. The results suggest that the anthropic driving-forces caused greater differences in pedogenesis than the soil location in the landscape.

ABSTRACT Weathering and pedogenesis have been studied for a wide range of rocks and climates around the world. However, the eruption of rhyolitic magmas is a rare geological event, which leads to few studies associated with the rhyolite-soil-landscape relationship. In this context, this study evaluated the influence of rhyolite weathering on the properties of soils along a slope in an Atlantic Forest environment in the state of Pernambuco, northeastern Brazil. Four weathering profiles derived from rhyolites were classified and sampled for chemical, physical, mineralogical, micromorphological, differential thermal, and thermogravimetric analyses. The chemical properties reflect the original rock rich in felsic minerals, poor in bases, and the types of clay minerals. The clay fraction of the profiles consists mainly of 1:1 phyllosilicates and oxides, indicating intermediate weathering. However, variations in the degree of structure weathering were evidenced by the presence of partially preserved fragments of the original rock in the sand fraction of the soils. The tropical humid climate of the region influenced conversion of hematite to goethite through the xanthization process, and the subsurface drainage deficiency allowed the formation of halloysite in the lowest position of the landscape. Because it is an acid rock with an aphanitic texture and porphyritic relative size of crystals, rhyolite weathering resulted in the formation of dystrophic soils, with predominance of quartz in the silt fraction. From the top to the lower third of the slope, a Haplic Cambisol, an Abruptic Lixisol, and two Haplic Lixisols were formed.

RESUMO O Cerrado piauiense tem grande importância econômica por ser uma área de expansão agrícola, sendo o quarto mais importante do Brasil e o primeiro do Nordeste. Representa 5,9 % do cerrado brasileiro, 36,9 % do nordestino e 46 % da área total do Estado do Piauí, ao todo são 11,5 milhões de hectares . O objetivo desta pesquisa foi estudar os pedoambientes da Serra do Quilombo, localizada no cerrado piauiense, e identificar as classes de solos existentes de acordo com o Sistema Brasileiro de Classificação de Solos. A identificação dos solos consistiu na caracterização de perfis de solo ao longo de um transecto, com a avaliação e coleta de solos em áreas de vegetação nativa, em três pontos, sendo nas extremidades e no centro da chapada . A análise dos solos e a coleta de amostras de cada horizonte dos três perfis de solo foram realizadas mediante abertura de trincheiras, com 2 m de profundidade. Foi feita a caracterização morfológica, física, química e mineralógica de cada perfil dos solos, juntamente com avaliação da influência dos fatores pedogenéticos na sua formação e evolução. Os solos estudados são formados de materiais de origem da mesma formação geológica, no entanto, com diferentes contribuições das diversas rochas, envolvendo arenitos e folhelhos. As características dos solos verificadas na Serra do Quilombo não diferem do padrão comumente observado nas chapadas do Brasil, sendo os perfis classificados como LATOSSOLOS AMARELOS Distróficos argissólicos, de acordo com o Sistema Brasileiro de Classificação de Solos.

ABSTRACT The savanna woodlands of Piauí state has great economic importance since it is an area for agricultural expansion, being the fourth most important of Brazil and the first from Brazilian Northeastern. The area accounts for 5.9% of the Brazilian savanna woodlands and 36.9% of the Northeastern savanna, covering 46% of the Piauí state area, in a total of 11.5 million hectares. The goal of this research was to study pedoenvironments of Serra do Quilombo region, which is in Piauí state savanna, as well as identifying existing soil classes, according to the Brazilian System of Soil Classification - SiBCS. Soil identification consisted in characterizing soil profiles along a transect, assessing in-field conditions and collecting soil samples, in areas of native vegetation. The samples were gathered from three distinct points, being two at the edges and one at the center of the plateau. Soil analyses were carried out with samples collected from each horizon through trench digging up to a 2-m depth. Morphological, physical, chemical and mineralogical characterizations were performed for each soil profile, along with an evaluation of the effect of pedogenic factors on their formation and development. All soils under study were formed with source materials of the same geological formation; however, each rock has a distinct contribution to the process, involving sandstones and shales. The characteristics observed in the soil from Serra do Quilombo have no difference from the pattern found in the Brazilian plateaus, and soil profiles were classified as dystrophic clayey Yellow Latosols (Oxisols), according to the SiBCS.

ABSTRACT The semiarid region of northeastern Brazil has a large area occupied by Planosols, where in the State of Pernambuco these soils are mainly used for livestock farming and subsistence crops. The knowledge on these soils is limited, which compromises the understanding on their behavior, potentialities and limitations.This study aimed to analyze morphological, chemical, physical and mineralogical attributes of Planosols developed under different geoenvironmental conditions. Morphological descriptions and chemical, physical and mineralogical analyses were performed in four profiles of Planosols along a rainfall gradient. An increase in rainfall allowed for an increase in the clay content in the Bt horizon and a reduction in ESP, EC, Na+, CEC, S, pH (water and KCl) and soil density. Horizons A and E were thicker in Planosols in more humid environments. The increase in ESP associated with the presence of expansive minerals (smectite and vermiculite) allowed the development of a prismatic structure in Haplic Planosols and a columnar structure in Natric Planosols. The mineralogical assembly is indicative of poorly weathered soils. The mineralogical assemblies of the silt and clay fractions were similar in the different geoenvironments, while higher contents of easily alterable minerals were observed in the composition of the sand fraction in environments with a drier climate.