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ABSTRACT Soil saturated hydraulic conductivity (Ksat) and steady-state infiltration rate (SSIR) are essential and necessary soil properties for different geoscience applications. Values of these hydraulic properties for the Brazilian territory are difficult to access and are dispersed in research efforts carried out around the country. This study developed an easy-to-manipulate, freely accessible database of soil saturated hydraulic conductivity, comprising field and laboratory analyses, and steady-state infiltration rates for Brazilian soils. This database was named Ksat-SSIR-DB. One analysis of the Ksat-SSIR-DB aimed to evaluate its coverage in Brazilian territory and in different soil groups. Average values of these hydraulic properties were also presented for textural classes, with values compared to those reported in international literature, and for other groupings, such as soil class, land use class, and porosity class. The variability of Ksat data in these groupings and in their combinations were also analyzed. The Ksat-SSIR-DB showed broad national coverage, comprising a total of 2,579 records, corresponding to 409 sampling sites, with Ksat and/or SSIR data and other associated soil information. A significant difference was observed between Ksat values for the vast majority of Brazilian clayey and very clayey soils compared to soils from the same textural groups from temperate regions. The two groupings that presented the lowest variability in terms of Ksat standard deviation values were the combination of textural classes with soil classes at the second category level of SiBCS (Brazilian Soil Classification System), and porosity classes with soil classes at the second category level of SiBCS. The Ksat-SSIR-DB has enormous potential for developing and testing Ksat pedotransfer functions in Brazilian soils, serving as a reference source for different geoenvironmental applications and, in particular, for modeling land surface processes. It is open access and can be accessed at https://www.sgb.gov.br/ksat-ssir-dbbase-de-dados-de-condutividade-hidraulica-saturada-e-de-taxa-de-infiltracao-basica-emsolos-brasileiros, which also includes the python script for data analysis.

https://doi.org/10.36783/18069657rbcs20240003

Evaluación y comprensión de la contaminación por arsénico en suelos agrícolas y sedimentos lacustres de la parroquia Papallacta, Ecuador, a través de índices ecotoxicológicos
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Jiménez, Paúl Andrés Díaz, Ximena Naves Silva, Marx Leandro Vega, Anyela Macêdo Medeiros, Beatriz Curi, Nilton

Siembra

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apr 2024, Volume 11 Suppl. 3 elocation e6628

Abstract: Es | Text: Es | PDF: Es

Effectiveness of proximal and remote sensing to trace soils spatial variability: A study case in a Brazilian Cerrado coffee farm
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Ribeiro, Diego

; Bócoli, Fernanda Almeida

; Pádua, Eduane José de

; Teixeira, Anita Fernanda dos Santos

; Guilherme, Luiz Roberto Guimarães

; Menezes, Michele Duarte de

; Curi, Nilton

; Silva, Sérgio Henrique Godinho

Ciência e Agrotecnologia

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2024, Volume 48 elocation e013824

Abstract: En Pt | Text: En Pt | PDF: En | PDF: Pt

ABSTRACT Brazil has made notable advances in soil mapping compared to other Latin American countries, driven by collaborative efforts from federal agencies, research institutions, and universities. However, detailed soil maps remain limited, particularly at local scales. This study explored soil spatial variability in a coffee plantation located in the Brazilian Cerrado, assessing the effectiveness of integrating proximal and remote sensing data to create detailed soil maps that support precision agriculture. Soil samples were collected from multiple depths across the study area and analyzed for texture, fertility, and elemental composition using portable X-ray fluorescence (pXRF). Additionally, terrain attributes derived from a digital elevation model were examined to understand their relationship with soil properties. Our results demonstrated that elements associated with parent material, such as Fe, Si, Ti, Al, and Ca, were more reliable indicators for distinguishing soil classes than topographic features. The dominance of Cambissolos Háplicos (CX), which have lower clay content and contain gravel, suggested a reduced need for soil amendments compared to Latossolos Vermelhos (LV), leading to potential cost savings for producers. These findings underscore the utility of pXRF in detecting soil variability and emphasize that combining proximal and remote sensing data can enhance the efficiency and sustainability of agricultural management.

RESUMO Embora o Brasil tenha avançado significativamente no mapeamento de solos, especialmente em comparação a outros países da América Latina, os mapas detalhados que auxiliam no manejo de precisão ainda são escassos. Este estudo analisou a variabilidade espacial do solo em uma fazenda de café no Cerrado brasileiro, avaliando a eficácia de dados de sensoriamento proximal e remoto para a criação de mapas detalhados que possibilitem a agricultura de precisão. Foram coletadas amostras de solo em diferentes profundidades e analisadas quanto à textura, fertilidade e composição elementar por meio de fluorescência de raios-X portátil (pXRF). Adicionalmente, atributos de terreno, gerados a partir de um modelo digital de elevação, foram utilizados para investigar a relação com as características do solo. Os resultados mostraram que os elementos associados ao material de origem do solo, como Fe, Si, Ti, Al e Ca, foram mais eficientes na diferenciação das classes de solo do que as variações topográficas. Observou-se uma predominância de Cambissolos Háplicos (CX), que se destacam pelo menor teor de argila e presença de cascalhos, sugerindo uma necessidade reduzida de corretivos e adubações quando comparados aos Latossolos Vermelhos (LV), o que pode representar economia para os produtores. Os resultados deste estudo destacam o potencial do pXRF em identificar a variabilidade do solo e indicam que a integração de dados de sensoriamento proximal e remoto pode contribuir para práticas agrícolas mais sustentáveis e econômicas.

https://doi.org/10.1590/1413-7054202448013824

Disposal of solid waste from civil construction: a screening proposal for a suitability system and case study in Nepomuceno, Minas Gerais
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Costa, Luana Sousa

; Pelegrino, Marcelo Henrique Procópio

; Villela, Bruno Silva

; Monteiro, Maria Eduarda Carvalho

; Vilela, Raísa Brito

; Pedroso, Daniela de Fátima

; Naime, Iris Helena Antunes

; Leite, Ivan Massimo Pereira

; Silva, Bruno Montoani

; Curi, Nilton

; Menezes, Michele Duarte de

Revista Brasileira de Ciência do Solo

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2024, Volume 48 elocation e0230044

Abstract: En | Text: En | PDF: En

ABSTRACT Most Brazilian municipalities do not have regulated areas for solid waste disposal in civil construction. Usually, residues are disposed of vacant lots and dumps, posing risks to the population health and the environment. Soils are the primary means for the disposal or recycling of waste, highlighting the importance of well-characterized soils and their respective landscape. This study aimed to establish a land suitability system for solid residues in civil construction and apply such information in a case study in Southeastern Brazil. An unprecedented digital soil map with a resolution of 30 m was created using the random forest classifier algorithm and soil field prospection information. A guide listing favorable soil-landscape attributes that most prevent soil erosion, water bodies or water table contamination was elaborated and discussed. Thus, such information was linked through a suitability system to classify areas with potential for receiving waste on a daily volume basis as follows: large size: >500 m³ day-1, medium size: >100 m³ day-1 and <300 m³ day-1, and small size <100 m³ day-1. Topography and soil depth were the most limiting factors of the areas in the case study. The proposed attributes as criteria for the suitability system complement the current state legislation. A total of 236 ha closer to the urban perimeter connected by roads in good condition were classified as suitable for managing medium- and small-scale daily volume, whose destination might reduce transportation and installation costs in the study area.

https://doi.org/10.36783/18069657rbcs20230044

Nonlinear models for soil moisture sensor calibration in tropical mountainous soils
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Silva, Bárbara Pereira Christofaro

; Tassinari, Diego

; Silva, Marx Leandro Naves

; Silva, Bruno Montoani

; Curi, Nilton

; Rocha, Humberto Ribeiro da

Scientia Agricola

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2022, Volume 79 N. 4 elocation e20200253

Abstract: En | Text: En | PDF: En

ABSTRACT Electromagnetic sensors are widely used to monitor soil water content (θ); however, site-specific calibrations are necessary for accurate measurements. This study compares regression models used for calibration of soil moisture sensors and investigates the relation between soil attributes and the adjusted parameters of the specific calibration equations. Undisturbed soil samples were collected in the A and B horizons of two Ultisols and two Inceptisols from the Mantiqueira Range in Southeastern Brazil. After saturation, the Theta Probe ML2X was used to obtain the soil dielectric constant (ε). Several readings were made, ranging from saturation to oven-dry. After each reading, the samples were weighted to calculate θ (m3 m–3). Fourteen regression models (linear, linearized, and nonlinear) were adjusted to the calibration data and checked for their residue distribution. Only the exponential model with three parameters met the regression assumptions regarding residue distribution. The stepwise regression was used to obtain multiple linear equations to estimate the adjusted parameters of the calibration model from soil attributes, with silt and clay contents providing the best relations. Both the specific and the general calibrations performed well, with RMSE values of 0.02 and 0.03 m3 m–3, respectively. Manufacturer calibration and equations from the literature were much less accurate, reinforcing the need to develop specific calibrations.

https://doi.org/10.1590/1678-992x-2020-0253 191 downloads

Rainfall erosivity estimation: Comparison and statistical assessment among methods using data from Southeastern Brazil
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Cardoso, Dione Pereira

; Avanzi, Junior Cesar

; Ferreira, Daniel Furtado

; Acuña-Guzman, Salvador Francisco

; Silva, Marx Leandro Naves

; Pires, Fábio Ribeiro

; Curi, Nilton

Revista Brasileira de Ciência do Solo

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2022, Volume 46 elocation e0210122

Abstract: En | Text: En | PDF: En

ABSTRACT Rainfall erosivity (R factor) is one of the six factors of the Universal Soil Loss Equation, being calculated based on the product of rainfall kinetic energy multiplied by its 30-minute maximum intensity. However, the lack of detailed and reliable rainfall data in many parts of the world has driven the use of other methods to estimate rainfall erosivity based on daily, monthly or annual data. These methods still need to be assessed to determine if their estimates are consistent with the standard method for calculating rainfall erosivity. This study aimed to select a consistent method for such replacement in Brazilian conditions without access the rainfall intensity data. The tested methods included: modified Fournier, MF; modified Fournier by Zhang, MF-Z; modified Fournier by Men, MF-M; Rainfall Disaggregation, RD; TRMM Satellite with modified Fournier coefficient, TRMM-F; and TRMM Satellite with monthly rainfall, TRMM-M. The rainfall data were obtained from the USP Meteorological Station, referring to the period from 2009 to 2015. The analyses were performed according to the Additive Main effects and Multiplicative Interaction (AMMI) model and Scott-Knott statistical tests. Considering the 1:1 line, all methods had a good adjustment, presenting similar behavior in relation to the standard method. The methods behaved differently for monthly and annual periods. The MF method proved to be capable of consistently replacing the standard method in all aforementioned situations. Considering the driest period, any method can be used. For annual rainfall erosivity estimation, the RD, MF, TRMM-F and TRMM-M methods can be applied; highlighting that the TRMM-based methods are optimal for locations without on-site rain gauges. Additionally, it was computed that the modified Fournier by Men and the modified Fournier by Zhang underestimated and overestimated the rainfall erosivity, respectively.

https://doi.org/10.36783/18069657rbcs20210122

Macro scale analysis of Syrah vineyards under winter growing cycles: Agronomical and ecophysiological responses
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Brant, Luciana Alves Caldeira

; Souza, Cláudia Rita de

; Mota, Renata Vieira da

; Fernandes, Fernanda de Paula

; Gonçalves, Mariana Gabriele Marcolino

; Menezes, Michele Duarte de

; Peregrino, Isabela

; Curi, Nilton

; Regina, Murillo de Albuquerque

Scientia Agricola

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2021, Volume 78 N. 6 elocation e20200055

Abstract: En | Text: En | PDF: En

ABSTRACT: In Southeast Brazil, the change of grape harvest from wet summer to dry winter through double-pruning management has improved the quality of wines, currently denominated winter wines. In order to better understand the influences of soil, macroclimate, and vineyard management in winter wines, we investigated seven vineyards in the states of Minas Gerais (Três Corações – TC, Três Pontas – TP, Cordislândia – COR, São Sebastião do Paraíso – SSP and Andradas – AND) and São Paulo (Itobi – ITO and Espirito Santo do Pinhal – PIN) during three consecutive growing seasons. The vineyards are located in warm temperate zones and grouped in four soil types: Acrudox in TC, AND and SSP, Hapludox in TP; Hapludult in AND and PIN; Eutrudept in ITO. The high clay content (> 35 %) observed in all soil types, associated to low evapotranspiration demand, avoided the occurrence of severe water stress, as observed by the high values of leaf and stem water potential, stomatal conductance, photosynthesis, and transpiration. Differences in vigor were more related to vineyard management and did not affect grape composition. Among vineyards, parameters for berry quality from ITO, such as sugar and acidity, were more associated to high soil sand content and winter temperature. No significant differences were found in anthocyanins and total phenols of berries among vineyards, suggesting that the high thermal range and low precipitation during autumn-winter, historically observed in all municipalities, seemed to be the main factor for improvement of phenolic compounds.

https://doi.org/10.1590/1678-992x-2020-0055 798 downloads

Environmental degradation risk by water erosion in a water producer Colombian Andes basin
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Mellado, Daniel Enrique Guauque

; Mello, Carlos Rogério de

; Curi, Nilton

Ciência e Agrotecnologia

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2021, Volume 45 elocation e010021

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

RESUMO Mundialmente, a degradação do solo devido à erosão hídrica tem sido um dos maiores problemas ambientais nas regiões tropicais, especialmente sob as severas condições dos Andes. Este estudo objetiva detalhar o risco do solo à erosão hídrica numa bacia hidrográfica produtora de água, localizada nos Andes colombianos (Bacia do rio Combeima), usando o modelo RUSLE e discutindo como reduzir os processos erosivos nas condições ambientais da região (forte declividade, variabilidade climática, diferentes classes e propriedades de solos, e usos da terra). O modelo RUSLE foi aplicado com auxílio de SIG para estimar as taxas de erosão atual e potencial na bacia a partir de sua calibração para regiões montanhosas, identificando áreas mais vulneráveis à erosão hídrica. A taxa de erosão atual em 50,5% da área total da bacia é maior que 25 t ha-1 ano-1, o que significa que a bacia apresenta um risco muito alto à erosão hídrica, com 30,4% de sua área com risco severo (> 100 t ha-1 ano-1). Foi possível concluir que os atuais usos da terra e os sistemas de manejo do solo não têm sido efetivos na redução da erosão hídrica, principalmente em áreas com topografia muito declivosa, demonstrando a necessidade de planejamento sustentável para melhor controlar as perdas de solo, água, carbono orgânico, nutrientes e outros elementos (não-nutrientes) nesta região dos Andes tropicais.

ABSTRACT Globally, soil degradation by water erosion has become one of the major environmental problems in tropical regions, especially under the severe environmental conditions of the Andes. This study aims to detail the soil risk to degradation by water erosion in a water producer basin located in the Tropical Colombian Andes (Combeima River basin), applying the RUSLE model, discussing how to minimize the erosion processes under its environmental conditions (steep slope, climatic variability, soil classes and properties diversity, and alternative land uses). RUSLE was applied with the support of GIS to estimate current and potential risk to soil erosion in the basin, allowing the identification of areas more prone to degradation. It was found that currently, 50.5% of the basin’s area presents, on average, annual soil losses greater than 25 Mg ha-1 yr-1, meaning a very high risk to water erosion, with 30.4% showing a severe risk (> 100 Mg ha-1 yr-1). It was possible to conclude that the current land uses and soil management systems have not been effective in mitigating soil erosion, mainly when situated in steep topography. Therefore, it is necessary sustainable planning for the conservation of soil, water, organic carbon, plant nutrients, and other elements (not-nutrients) in this tropical Andes region.

https://doi.org/10.1590/1413-7054202145010021 281 downloads

Digital soil mapping: Predicting soil classes distribution in large areas based on existing soil maps from similar small areas
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Gonçalves, Thaís Gabriela

; Pons, Nívea Adriana Dias

; Melloni, Eliane Guimarães Pereira

; Mancini, Marcelo

; Curi, Nilton

Ciência e Agrotecnologia

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2021, Volume 45 elocation e007921

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

RESUMO Há uma crescente demanda por mapas de solo, já que informações detalhadas de solos estão diretamente relacionadas com agricultura, urbanização e conservação ambiental. Porém, há escassez de mapas de solo em grande escala em países tropicais em desenvolvimento como o Brasil. Apesar de existirem mapas para pequenas áreas, grandes regiões possuem mapas pouco detalhados. Considerando-se a importância de se buscarem alternativas para superar a falta de informações detalhadas de solo, o objetivo deste trabalho foi extrapolar mapas locais para áreas maiores semelhantes que necessitam de informações mais detalhadas. A bacia do rio Anhumas, no município de Itajubá, sudeste do Brasil, foi manualmente mapeada e este mapa foi utilizado para predizer a distribuição de solos para todo o município. Primeiro, o modelo de predição foi testado na mesma bacia e alcançou acurácia global de 67% e coeficiente Kappa de 0,62. Depois, os resultados foram usados conjuntamente com dados da bacia José Pereira para predizer as classes de solo de todo o município, alcançando acurácia global de 54% e coeficiente Kappa de 0,40. Dados de material de origem em baixa resolução confundiram os modelos; as predições obtiveram melhores resultados quando esta variável foi removida. O mapa de solos de Minas Gerais apresenta apenas a classe de solo Argissolo e suas associações com outros solos para a área. O mapa confeccionado por este trabalho, porém, identificou mais classes de solo. O mapeamento de áreas representativas e sua extrapolação para áreas maiores constitui alternativa promissora para superar a escassez de mapas detalhados de solo.

ABSTRACT There is an ever-growing need for soil maps, since detailed soil information is directly related to agricultural activities, urbanization and environmental protection. However, there is a lack of large-scale soil maps in developing tropical countries such as Brazil. Albeit there are soil maps for small areas, large regions usually have undetailed maps. Considering the importance of finding low-cost alternatives to overcome the lack of detailed soil information, the main objective of this work was to manually create a local soil map and extrapolate it to similar larger areas that lack detailed soil information. The Anhumas River Basin, in the municipality of Itajubá, southeast Brazil, was manually mapped and this map was used to predict soils distribution for the entire municipality. First, the prediction model was tested in the same basin and provided sufficient results, achieving 67% global accuracy and 0.62 Kappa coefficient. Second, the resulting map was used together with the soil map of the larger José Pereira Basin to map the entire municipality, achieving 54% global accuracy and 0.40 Kappa coefficient. Low resolution parent material information was found to confuse models; maps showed better results when this variable was removed. The Minas Gerais soil map presents general mapping units only for the Acrisol class and its associations with other soil classes in the area. The soil map predicted by this work identified more soil classes. Mapping representative areas and extrapolating these maps to larger similar areas constitute a promising alternative to overcome the lack of detailed soil maps.

https://doi.org/10.1590/1413-7054202145007921 176 downloads

10.

X-ray fluorescence spectrometry applied to digital mapping of soil fertility attributes in tropical region with elevated spatial variability
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BENEDET, LUCAS

; NILSSON, MATHEUS S.

; SILVA, SÉRGIO HENRIQUE G.

; PELEGRINO, MARCELO H.P.

; MANCINI, MARCELO

; MENEZES, MICHELE D. DE

; GUILHERME, LUIZ ROBERTO G.

; CURI, NILTON

Anais da Academia Brasileira de Ciências

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2021, Volume 93 N. 4 elocation e20200646

Abstract: En | Text: En | PDF: En

Abstract Portable X-ray fluorescence (pXRF) spectrometry offers valuable information for prediction models of soil fertility attributes spatial variation, although this approach is yet scarce in tropical regions. This study aims to predict and build spatial variability maps of soil pH, remaining phosphorus (P-Rem), soil organic matter (SOM) and sum of bases (SB) using pXRF results through stepwise multiple linear regression (SMLR) and Random Forest (RF) in a highly variable tropical area. Composite samples from soil A horizon were collected at 90 points throughout the campus of the Federal University of Lavras, Minas Gerais, Brazil, for pH, P-Rem, SOM, SB and pXRF analyses. RF predictions showed the highest accuracies, especially for P-Rem and SB (R² values of 0.66 and 0.55, respectively). Attributes that showed higher R² in punctual predictions also exhibited higher R² in spatial predictions. Data obtained from pXRF in tandem with RF can be used to assist prediction models for soil fertility attributes, consequently enabling the digital mapping of such attributes and helping to improve the knowledge about the spatial variability of such attributes in soils of tropical climate. This technique can therefore assist in the identification and orientation of adequate management practices in tropical agricultural practices.

https://doi.org/10.1590/0001-3765202120200646 81 downloads

11.

Study of an abnormal occurrence of Oxisols in strongly undulated relief in the south of Minas Gerais, Brazil, with support of pXRF and geomorphology
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Bócoli, Fernanda Almeida

; Santos, Walbert Júnior Reis dos

; Silva, Sérgio Henrique Godinho

; Teixeira, Anita Fernanda dos Santos

; Mancini, Marcelo

; Curi, Nilton

Ciência e Agrotecnologia

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2021, Volume 45 elocation e018121

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

RESUMO Latossolos são os principais solos do Brasil e classicamente ocorrem em superfícies geomórficas suavizadas e estáveis. No entanto, no Sul de Minas Gerais, Latossolos têm sido observados em relevo forte ondulado, uma condição rara para estes solos nesta região fisiográfica. Este trabalho teve como objetivo acessar a dinâmica elementar e o relevo com uso de espectrometria de fluorescência de raios-X portátil (pXRF), em associação à geomorfologia, para entender tal ocorrência. Os solos estudados estão localizados no município de Muzambinho, Estado de Minas Gerais, Brasil. Perfis de Latossolo foram caracterizados no terço superior (P1), terço médio (P2) e terço inferior (P3) da encosta. Após a descrição morfológica, amostras de solo foram coletadas nos horizontes A, AB e Bw dos perfis. Foram realizadas análises físicas, químicas e espectrométricas dos solos em laboratório. Os teores de Ti e Fe (pXRF) tiveram alta correlação com as frações texturais dos solos. Foram encontrados altos graus de intemperismo-lixiviação dos Latossolos, embora ocorram em encosta íngreme onde solos mais jovens (Cambissolos) seriam esperados. A concordância de altitude dos topos observada nas áreas circundantes mais elevadas indica um paleorrelevo plano, ajudando a explicar esta ocorrência anormal. Os valores dos índices de intemperismo dos solos diminuíram ao longo da encosta, indicando o enriquecimento de sílica por escoamento superficial e fluxo de água subsuperficial nas posições mais baixas da paisagem. As análises de pXRF ajudaram na caracterização destes solos velhos em topografia forte ondulada. O equipamento forneceu bases para confirmação dos seus altos graus de intemperismo, além de detectar evidências do pré-intemperismo do regolito dessa paisagem muito antiga.

ABSTRACT Oxisols are the main soils in Brazil and they classically occur in stable and gentle geomorphic surfaces. However, in the south of Minas Gerais State, Oxisols have been observed under strongly undulated relief, a very rare condition for these soils in this physiographic region. Therefore, this work aimed to assess the elemental dynamics and relief enhanced with portable X-ray fluorescence (pXRF) spectrometry, associated to geomorphology, to understand such occurrence. The studied soils are located in Muzambinho municipality, Minas Gerais State, Brazil. Oxisol profiles were characterized in the upper third (P1), middle third (P2) and lower third (P3) of the hillslope. After morphological description, soil samples were collected in the A, AB and Bo horizons of the profiles. Physical, chemical and pXRF analyses of the soils were carried out in the laboratory. Ti and Fe content (pXRF) had a high correlation with the soil textural fractions. High weathering-leaching degrees were determined, although they occur on a steep slope where younger soils (Inceptisols) would be expected in this region. The altitudinal concordance of summits observed in the more elevated surrounding areas indicates a flat paleorelief, helping to explain this unusual occurrence. The soils’ weathering degree values decreased down the hillslope, indicating silica enrichment through runoff and subsuperficial water flux in the lower landscape positions. The pXRF analyses assisted the characterization of these old soils occurring in steep relief. It provided bases for confirming their high weathering degree indexes and detected evidences of the pre-weathering of the regolith of this very old landscape.

https://doi.org/10.1590/1413-7054202145018121 1 downloads

12.

Hydrosedimentological modeling in a headwater basin in Southeast Brazil
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Mauri, Eliete Nazaré Eduardo

; Viola, Marcelo Ribeiro

; Norton, Lloyd Darrell

; Owens, Phillip Ray

; Mello, Carlos Rogério de

; Pinto, Leandro Campos

; Curi, Nilton

Revista Brasileira de Ciência do Solo

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2020, Volume 44 elocation e0200047

Abstract: En | Text: En | PDF: En

ABSTRACT Hydrosedimentological modeling is a useful tool to predict the water dynamic in a basin and for water resources management. This study aimed to i) evaluate the ability of Soil and Water Assessment Tool (SWAT) to model sediment load and continuous monthly streamflow in the Mortes River Basin (MRB) in Southeastern Brazil; ii) estimate the sediment yield spatially distributed by sub-basins; iii) estimate the sediment load export to the Funil Hydroelectric Power Plant reservoir (FHPP), located in the MRB outlet. For the sensitivity analysis, calibration, and uncertainty analysis of the model, a semi-automatic calibration in SWAT-CUP version 5.1.6 software with the “Sequential Uncertainty Fitting” algorithm was used. To evaluate the ability of SWAT to reproduce the continuous MRB monthly streamflow and sediment load, statistical indexes, and graphical analyses were used to compare the simulated and observed data. For the sediment evaluation, a spatial and temporal comparison of sediment yield maps was used as well as the sediment yield observed in sub-basins, aiming to identify the areas with a more significant contribution to the sediment generation in the basin. The results demonstrated that SWAT performed satisfactorily in simulating both monthly sediment load and streamflow. For discharge calibration, 99 % of the measured data were bracketed by the 95 % prediction uncertainty (95PPU), and for validation, 97 % of the data were bracketed by the 95PPU, which indicates proper bracketing of the measured data within model prediction uncertainty. Uncertainty analysis indicated that 95PPU could capture 78 % of the sediment loads measured during the calibration and 72 % of the measured data during the validation period at MRB. The hydrologic response unit with pasture and Argissolos (Ultisols), Neossolos Litólicos (Entisols), and Cambissolos (Inceptisols) combined with undulated relief were the main areas responsible for the highest sediment contributions. The sediment load delivered to the reservoir from its filling 2002 to 2015 was estimated in 6,682,704 m3 (16,706,761 Mg) (density of 2.5-Mg m-3) which value corresponded to 2.6 % of storage capacity (water plus sediment) in 14 years. These results are strategic since to become feasible identifying priority areas for soil and water conservation practices as well as useful information for water resources planning and management in the studied basin.

https://doi.org/10.36783/18069657rbcs20200047 226 downloads

13.

How sulfate content and soil depth affect the adsorption/desorption of selenate and selenite in tropical soils?
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Araujo, Anderson Mendes

; Lessa, Josimar Henrique de Lima

; Chanavat, Luiz Gustavo

; Curi, Nilton

; Guilherme, Luiz Roberto Guimarães

; Lopes, Guilherme

Revista Brasileira de Ciência do Solo

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2020, Volume 44 elocation e0200087

Abstract: En | Text: En | PDF: En

ABSTRACT Sorption of selenate (SeO 4 2- ) and selenite (SeO 3 2- ) is poorly understood in Brazilian agroecosystems, especially in soils from agricultural areas containing different contents of competing anions, such as sulfate (SO 4 2- ). This study aimed to assess the sorption behavior of selenate and selenite at different soil layers of a tropical soil treated with different rates of agricultural gypsum (thus, containing different contents of sulfate), collected under a coffee plantation. Soil samples from an experimental area where phosphogypsum has been previously applied at different rates (0, 7, 14, and 56 t ha -1 ) were taken at the following soil layers: 0.15-0.25, 0.35-0.45, and 1.25-1.35 m. Adsorption experiments were carried out adding 20 mL of solutions containing 100 and 500 μg L -1 of selenate and 10 and 15 mg L -1 of selenite to 2 grams of soil. Desorption experiments were also performed using a soil:solution ratio of 1:10. Adsorption of selenate increased with soil depth and decreased upon increasing sulfate contents in the soil, by contrast, selenite was consistently adsorbed at higher contents - when compared with selenate - at any soil depth and its sorptive behavior was not affected by the presence of sulfate. Furthermore, selenite was less desorbed than selenate under all conditions. In conclusion, selenite is much more retained in tropical soils and less available to plants than selenate. Also, although sulfate has shown to be able to hinder selenate retention, it has no substantial effect on the sorption behavior of selenite in tropical agroecosystems.

https://doi.org/10.36783/18069657rbcs20200087 336 downloads

14.

Monitoring land use impacts on sediment production: a case study of the pilot catchment from the Brazilian program of payment for environmental services
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Bispo, Diêgo Faustolo Alves

; Batista, Pedro Velloso Gomes

; Guimarães, Danielle Vieira

; Silva, Marx Leandro Naves

; Curi, Nilton

; Quinton, John Norman

Revista Brasileira de Ciência do Solo

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2020, Volume 44 elocation e0190167

Abstract: En | Text: En | PDF: En

ABSTRACT Through the lack or non-use of conservationist criteria for adequate land use and management, the scarcity of natural resources becomes ever more evident. This study aimed to analyze the origin of the sediments in the Posses catchment, municipality of Extrema, state of Minas Gerais, Brazil, throughout the fingerprinting technique and portable X-ray fluorescence. Samples from soils under agriculture, pasture, and roads; and from the subsoil of theses land uses were taken in a widespread and representative manner from the entire Posses catchment. Lag deposits and river bed sediment samples were collected downstream from the catchment outlet. A total of 45 geochemical elements were analyzed in the samples by a portable X-ray fluorescence device (pXRF). The outlier test, Kruskal-Wallis test, multivariate discriminant analysis, and a mixing model were used to estimate the contribution of each source in relation to the sediments that arrive at the mouth of the catchment. The elements selected as geochemical tracers were Sr, Al2O3, Ba, Rb, Ti, Fe, and Zn, which combined correctly discriminated 81 % of the sediment sources. The largest and smallest proportion of sediment from the Posses catchment outlet comes from rural roads and agriculture, respectively. The contribution of the subsoil was higher for lag deposits or lower for river bed sediments, than the pasture. There was a low degree of uncertainty (<8 %) for predictions made by the model employed. The types of use, selected as potential sediment sources in the Posses catchment, are adequately discriminated through the geochemical tracers quantified through the pXRF. The fingerprinting technique estimates that the contributions to outlet sediments are dominated by rural roads, following by subsoil or pasture (depending on the type of sediment evaluated) and by agriculture. The sediment sampling strategies used in this study provided similar results for the period studied. Our results showed the potential of the fingerprinting technique and the pXRF for use as tools by the program of Payment for Environmental Services in the monitoring of catchment areas.

https://doi.org/10.36783/18069657rbcs20190167 526 downloads

15.

Modeling and prediction of sulfuric acid digestion analyses data from PXRF spectrometry in tropical soils
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Silva, Sérgio Henrique Godinho

; Silva, Elen Alvarenga

; Poggere, Giovana Clarice

; Pádua Junior, Alceu Linares

; Gonçalves, Mariana Gabriele Marcolino

; Guilherme, Luiz Roberto Guimarães

; Curi, Nilton

Scientia Agricola

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2020, Volume 77 N. 4 elocation e20180132

Abstract: En | Text: En | PDF: En

ABSTRACT Sulfuric acid digestion analyses (SAD) provide useful information to environmental studies, in terms of the geochemical balance of nutrients, parent material uniformity, nutrient reserves for perennial crops, and mineralogical composition of the soil clay fraction. Yet, these analyses are costly, time consuming, and generate chemical waste. This work aimed at predicting SAD results from portable X-ray fluorescence (pXRF) spectrometry, which is proposed as a “green chemistry” alternative to the current SAD method. Soil samples developed from different parent materials were analyzed for soil texture and SAD, and scanned with pXRF. The SAD results were predicted from pXRF elemental analyses through simple linear regressions, stepwise multiple linear regressions, and random forest algorithm, with and without incorporation of soil texture data. The modeling was developed with 70 % of the data, while the remaining 30 % was used for validation through calculation of R2, adjusted R2, root mean square error, and mean error. Simple linear regression can accurately predict SAD results of Fe2O3 (R2 0.89), TiO2 (R2 0.96), and P2O5 (R2 0.89). Stepwise regressions provided accurate predictions for Al2O3 (R2 0.87) and Ki - molar weathering index (SiO2/Al2O3) (R2 0.74) by incorporating soil texture data, as well as for SiO2 (R2 0.61). Random forest also provided adequate predictions, especially for Fe2O3 (R2 0.95), and improved results of Kr - molar weathering index (SiO2/(Al2O3 + Fe2O3)) (R2 0.66), by incorporation of soil texture data. Our findings showed that the SAD results could be accurately predicted from pXRF data, decreasing costs, time and the production of laboratory waste.

https://doi.org/10.1590/1678-992x-2018-0132 968 downloads

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