Nonlinear models for soil moisture sensor calibration in tropical mountainous soils

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.

Soil catenas in a pilot sub-basin in the region of Itajubá, Minas Gerais state, Brazil, for environmental planning / Catenas de solo em sub-bacia piloto na região de Itajubá, Minas Gerais, Brasil, para planejamento ambiental

Systemic studies that allow the environmental characterization of pilot sub-basins are essential to guide their management, which are the basis for adequate environmental planning. The José Pereira sub-basin has an area of approximately 40 km² and is located in the municipality of Itajubá, south of the state of Minas Gerais, Brazil. This area was chosen as a pilot sub-basin for this study because it holds an important forest remnant, the Serra dos Toledos Biological Reserve, and part of the urban area of the municipality in the process of expansion, as well as a rural area where inappropriate and intensive agricultural activities are practiced. In this scenario, this atudy examined the soil catenas of this sub-basin to serve as an important instrument of planning for this unit. Eight soil catenas distributed into three topo-morphological compartments were studied. According to the generated soil map, Haplic Cambisols occupy 26% of the sub-basin, in mountainous relief; Red and Red-Yellow Latosols, 6% of the area, predominating in the flat-to undulating relief; Haplic Gleysols, 7% of the area, in the lowlands, in flat relief and at the footslope. Finally,Red and Red-Yellow Argisols were the predominant classes, occurring in almost 50% of the sub-basin, underundulating and strongly undulating reliefs. Based on the combined results, a model of local evolution of the sub-basin soils was proposed: the younger soils, Haplic Cambisol and Haplic Gleysol, occupy the positions of convex top and floodplain, respectively. In the upper and lower thirds of the landscape, the predominance of Red Argisol is related to constant renewal of soil material, preventing it from reaching the latosolic stage. In addition, part of these Argisols has a Bw horizon below Bt horizon in rugged relief. Moreover, in the landscape lower third, Latosols are present, even in areas with steep slope.

Estudos sistêmicos que possibilitem a caracterização ambiental de sub-bacias hidrográficas pilotos são essenciais para direcionar sua gestão, sendo fundamentais para um adequado planejamento ambiental. A sub-bacia José Pereira possui uma área aproximada de 40 km² e se insere no município de Itajubá, sul do Estado de Minas Gerais, Brasil. Esta área foi escolhida como sub-bacia piloto para este estudo, pois possui um importante remanescente florestal, a Reserva Biológica Serra dos Toledos, assim como parte da área urbana do município em processo de expansão, além de uma área rural com uso de práticas agropecuárias inadequadas e intensivas. Desta forma, o presente trabalho teve como objetivo estudar as catenas de solos desta sub-bacia, para servir como importante instrumento de planejamento desta unidade. Oito catenas de solos distribuídas em três compartimentos topomorfológicos foram estudadas. De acordo com o mapa de solos gerado, os Cambissolos Háplicos ocupam 26% da sub-bacia, estando sob relevo montanhoso; os Latossolos Vermelho e Vermelho Amarelo, 6% da área, predominando no relevo plano a ondulado; os Gleissolos Háplicos, com 7% da área, estando nas baixadas, em relevo plano e nos sopés das encostas; e as classes dos Argissolos Vermelho e Vermelho Amarelo foram as predominantes, distribuídas por 56% da sub-bacia, ocupando relevo ondulado e forte ondulado. Com base nos resultados conjuntos obtidos propôs-se um modelo de evolução local dos solos da sub-bacia: os solos mais jovens, Cambissolo Háplico e Gleissolo Háplico, ocupam as posições de topo convexo e a planície de inundação, respectivamente. Nos terços superior e inferior da encosta ocorre o predomínio de Argissolo Vermelho, o qual está relacionado à renovação constante de material do solo, impedindo que o estágio latossólico seja atingido. Além disso, parte significativa desses Argissolos apresenta horizonte Bw abaixo do horizonte [...].

Soil catenas in a pilot sub-basin in the region of Itajubá, Minas Gerais state, Brazil, for environmental planning / Catenas de solo em sub-bacia piloto na região de Itajubá, Minas Gerais, Brasil, para planejamento ambiental

Systemic studies that allow the environmental characterization of pilot sub-basins are essential to guide their management, which are the basis for adequate environmental planning. The José Pereira sub-basin has an area of approximately 40 km² and is located in the municipality of Itajubá, south of the state of Minas Gerais, Brazil. This area was chosen as a pilot sub-basin for this study because it holds an important forest remnant, the Serra dos Toledos Biological Reserve, and part of the urban area of the municipality in the process of expansion, as well as a rural area where inappropriate and intensive agricultural activities are practiced. In this scenario, this atudy examined the soil catenas of this sub-basin to serve as an important instrument of planning for this unit. Eight soil catenas distributed into three topo-morphological compartments were studied. According to the generated soil map, Haplic Cambisols occupy 26% of the sub-basin, in mountainous relief; Red and Red-Yellow Latosols, 6% of the area, predominating in the flat-to undulating relief; Haplic Gleysols, 7% of the area, in the lowlands, in flat relief and at the footslope. Finally,Red and Red-Yellow Argisols were the predominant classes, occurring in almost 50% of the sub-basin, underundulating and strongly undulating reliefs. Based on the combined results, a model of local evolution of the sub-basin soils was proposed: the younger soils, Haplic Cambisol and Haplic Gleysol, occupy the positions of convex top and floodplain, respectively. In the upper and lower thirds of the landscape, the predominance of Red Argisol is related to constant renewal of soil material, preventing it from reaching the latosolic stage. In addition, part of these Argisols has a Bw horizon below Bt horizon in rugged relief. Moreover, in the landscape lower third, Latosols are present, even in areas with steep slope.(AU)

Estudos sistêmicos que possibilitem a caracterização ambiental de sub-bacias hidrográficas pilotos são essenciais para direcionar sua gestão, sendo fundamentais para um adequado planejamento ambiental. A sub-bacia José Pereira possui uma área aproximada de 40 km² e se insere no município de Itajubá, sul do Estado de Minas Gerais, Brasil. Esta área foi escolhida como sub-bacia piloto para este estudo, pois possui um importante remanescente florestal, a Reserva Biológica Serra dos Toledos, assim como parte da área urbana do município em processo de expansão, além de uma área rural com uso de práticas agropecuárias inadequadas e intensivas. Desta forma, o presente trabalho teve como objetivo estudar as catenas de solos desta sub-bacia, para servir como importante instrumento de planejamento desta unidade. Oito catenas de solos distribuídas em três compartimentos topomorfológicos foram estudadas. De acordo com o mapa de solos gerado, os Cambissolos Háplicos ocupam 26% da sub-bacia, estando sob relevo montanhoso; os Latossolos Vermelho e Vermelho Amarelo, 6% da área, predominando no relevo plano a ondulado; os Gleissolos Háplicos, com 7% da área, estando nas baixadas, em relevo plano e nos sopés das encostas; e as classes dos Argissolos Vermelho e Vermelho Amarelo foram as predominantes, distribuídas por 56% da sub-bacia, ocupando relevo ondulado e forte ondulado. Com base nos resultados conjuntos obtidos propôs-se um modelo de evolução local dos solos da sub-bacia: os solos mais jovens, Cambissolo Háplico e Gleissolo Háplico, ocupam as posições de topo convexo e a planície de inundação, respectivamente. Nos terços superior e inferior da encosta ocorre o predomínio de Argissolo Vermelho, o qual está relacionado à renovação constante de material do solo, impedindo que o estágio latossólico seja atingido. Além disso, parte significativa desses Argissolos apresenta horizonte Bw abaixo do horizonte [...].(AU)

Preconsolidation stress of gibbsitic and kaolinitic Oxisols under a multipractice conservationist coffee system / Pressão de pré-consolidação de Latossolos gibbsítico e caulinítico sob sistema de multipraticas conservacionista no cultivo cafeeiro

Our goal was to analyze the impact of a multipractice soil conservationist system on coffee production in tropical soils (LATOSSOLO VERMELHO-AMARELO caulinítico/kaolinitic Haplustox and LATOSSOLO VERMELHO-gibbsítico/gibbsitic Acrustox) in Minas Gerais, Brazil. In the experimental area, the soil management involved a set of multiple conservationist practices during cultivation for more than 3.5 yrs. Soil samples were collected at 0-5, 10-15, and 20-25 cm depths at two positions: planting rows and between rows. The soil physical and mechanical properties were determined, with a focus mainly on the preconsolidation stress model (preconsolidation stress versus matric tension). For the purpose of analysis, a split-split plot experimental design was implemented. A linear mixed regression model (LMR) was fitted, and Wald's test was performed (P < 0.05). An improvement of soil physical quality for both Oxisols was observed at the planting row position. The effects of multipractice soil management after 3.5 yrs of cultivation in association with increased gibbsite content could promote new soil structure organization, as revealed by LMR, resulting in more resilient soils (between rows) and increasing the resistance to external pressures on gibbsitic Acrustox. Overall, the findings herein are in concordance with global trends towards conservationist practices that may alleviate soil compaction in agricultural systems to maintain environmental sustainability.(AU)

Nosso objetivo foi analisar o impacto de um sistema de manejo do solo com multi-práticas conservacionistas para o cultivo cafeeiro em solos tropicais (LATOSSOLO VERMELHO-AMARELO caulinítico/ kaolinitic Haplustox and LATOSSOLO VERMELHO gibbsítico/ gibbsitic Acrustox) em Minas Gerais, Brasil. Na área experimental, o manejo do solo incluiu um conjunto de multi-práticas conservacionistas por mais de 3,5 anos. Amostras de solo foram coletadas em 0-5; 10-15; e profundidades de 20 a 25 cm em duas posições: linha e entrelinha. As propriedades físicas e mecânicas do solo foram determinadas, concentrando-se principalmente na modelagem da compactação (estresse de pré-consolidação versus tensão matricial). Para fins de análise, foi considerado o delineamento experimental de parcelas subsubdivididas. Foi ajustado o modelo de regressão linear mista (RLM), bem como o teste F de Wald (P < 0,05). Melhorias na qualidade física do solo em ambos os Latossolos foi observada na linha de plantio. Os efeitos do sistema de manejo multipráticas usado após 3,5 anos de cultivo associado ao maior conteúdo de gibbsita podem promover uma nova organização da estrutura do solo revelada pelo RLM, que resulta em solos mais resilientes (na entrelinha), melhorando a resistência às pressões externas aplicadas ao Latossolo gibbsítico. No geral, os resultados aqui apresentadas estão de acordo com as tendências globais em direção a práticas conservacionistas que podem aliviar a compactação do solo em sistemas agrícolas e manter a sustentabilidade ambiental.(AU)

Macro scale analysis of Syrah vineyards under winter growing cycles: Agronomical and ecophysiological responses

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.(AU)

Macro scale analysis of Syrah vineyards under winter growing cycles: Agronomical and ecophysiological responses

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.

Modeling and prediction of sulfuric acid digestion analyses data from PXRF spectrometry in tropical soils

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.

Tracing the origin of reservoir sediments using magnetic properties in Southeastern Brazil / Traçando a origem de sedimentos de reservatórios usando propriedades magnéticas no Sudeste do Brasil

Determining the origin of eroded soil is essential to design effective soil erosion control strategies which preserve the soil resource, enhance agricultural productivity, and reduce the negative impacts of soil erosion, in-field and off-field. Magnetic properties have been widely used in temperate environments to identify sediment sources, pathways and links, but there have been very few applications in tropical and subtropical environments. Therefore, in this paper we investigated reservoir sediment sources in the Upper Grande River Basin, Southeastern Brazil, using sediment tracing techniques based on magnetic parameters (low and high frequency magnetic susceptibility, frequency dependent susceptibility). The different parent materials and subtropical weathering conditions resulted in soils having different Fe oxide minerals and Fe oxide contents, promoting magnetic variability that allowed comparison and identification of possible sources of reservoir sediments in order to reduce water erosion impacts. The results indicate the suitability of magnetic properties as a tracer for soil erosion studies in tropical environments.

Determinar a origem de solos erodidos é essencial para projetar estratégias efetivas de controle da erosão do solo que preservem os recursos do solo, aumentem a produtividade agrícola e reduzam os impactos negativos da erosão do solo, em campo e fora dele. As propriedades magnéticas têm sido amplamente utilizadas em ambientes temperados para identificar fontes, vias e elos de sedimentos, mas existem pouquíssimas aplicações em ambientes tropicais. Portanto, neste trabalho investigamos fontes de sedimentos de reservatórios na Bacia do Alto Rio Grande, Sudeste do Brasil, utilizando técnicas de rastreamento de sedimentos baseadas em parâmetros magnéticos (suscetibilidade magnética de baixa e alta freqüência, susceptibilidade dependente da freqüência). Os diferentes materiais de origem e condições de intemperismo tropical resultaram em solos com diferentes minerais de óxido de Fe e teores de óxidos de Fe, promovendo variabilidade magnética que permitiu a comparação e identificação de possíveis fontes de sedimentos de reservatórios para reduzir os impactos da erosão hídrica. Os resultados indicam a adequação das propriedades magnéticas como um traçador para estudos de erosão do solo em ambientes tropicais.

Modeling and prediction of sulfuric acid digestion analyses data from PXRF spectrometry in tropical soils

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.(AU)

Tracing the origin of reservoir sediments using magnetic properties in Southeastern Brazil / Traçando a origem de sedimentos de reservatórios usando propriedades magnéticas no Sudeste do Brasil

Determining the origin of eroded soil is essential to design effective soil erosion control strategies which preserve the soil resource, enhance agricultural productivity, and reduce the negative impacts of soil erosion, in-field and off-field. Magnetic properties have been widely used in temperate environments to identify sediment sources, pathways and links, but there have been very few applications in tropical and subtropical environments. Therefore, in this paper we investigated reservoir sediment sources in the Upper Grande River Basin, Southeastern Brazil, using sediment tracing techniques based on magnetic parameters (low and high frequency magnetic susceptibility, frequency dependent susceptibility). The different parent materials and subtropical weathering conditions resulted in soils having different Fe oxide minerals and Fe oxide contents, promoting magnetic variability that allowed comparison and identification of possible sources of reservoir sediments in order to reduce water erosion impacts. The results indicate the suitability of magnetic properties as a tracer for soil erosion studies in tropical environments.(AU)

Determinar a origem de solos erodidos é essencial para projetar estratégias efetivas de controle da erosão do solo que preservem os recursos do solo, aumentem a produtividade agrícola e reduzam os impactos negativos da erosão do solo, em campo e fora dele. As propriedades magnéticas têm sido amplamente utilizadas em ambientes temperados para identificar fontes, vias e elos de sedimentos, mas existem pouquíssimas aplicações em ambientes tropicais. Portanto, neste trabalho investigamos fontes de sedimentos de reservatórios na Bacia do Alto Rio Grande, Sudeste do Brasil, utilizando técnicas de rastreamento de sedimentos baseadas em parâmetros magnéticos (suscetibilidade magnética de baixa e alta freqüência, susceptibilidade dependente da freqüência). Os diferentes materiais de origem e condições de intemperismo tropical resultaram em solos com diferentes minerais de óxido de Fe e teores de óxidos de Fe, promovendo variabilidade magnética que permitiu a comparação e identificação de possíveis fontes de sedimentos de reservatórios para reduzir os impactos da erosão hídrica. Os resultados indicam a adequação das propriedades magnéticas como um traçador para estudos de erosão do solo em ambientes tropicais.(AU)

Soil type spatial prediction from Random Forest: different training datasets, transferability, accuracy and uncertainty assessment

Different uses of soil legacy data such as training dataset as well as the selection of soil environmental covariables could drive the accuracy of machine learning techniques. Thus, this study evaluated the ability of the Random Forest algorithm to predict soil classes from different training datasets and extrapolate such information to a similar area. The following training datasets were extracted from legacy data: a) point data composed of 53 soil samples; b) 30 m buffer around the soil samples, and soil map polygons excluding: c) 20 m; and d) 30 m from the boundaries of polygons. These four datasets were submitted to principal component analysis (PCA) to reduce multidimensionality. Each dataset derived a new one. Different combinations of predictor variables were tested. A total of 52 models were evaluated by means of error of models, prediction uncertainty and external validation for overall accuracy and Kappa index. The best result was obtained by reducing the number of predictors with the PCA along with information from the buffer around the points. Although Random Forest has been considered a robust spatial predictor model, it was clear it is sensitive to different strategies of selecting training dataset. Effort was necessary to find the best training dataset for achieving a suitable level of accuracy of spatial prediction. To identify a specific dataset seems to be better than using a great number of variables or a large volume of training data. The efforts made allowed for the accurate acquisition of a mapped area 15.5 times larger than the reference area.

Soil type spatial prediction from Random Forest: different training datasets, transferability, accuracy and uncertainty assessment

Different uses of soil legacy data such as training dataset as well as the selection of soil environmental covariables could drive the accuracy of machine learning techniques. Thus, this study evaluated the ability of the Random Forest algorithm to predict soil classes from different training datasets and extrapolate such information to a similar area. The following training datasets were extracted from legacy data: a) point data composed of 53 soil samples; b) 30 m buffer around the soil samples, and soil map polygons excluding: c) 20 m; and d) 30 m from the boundaries of polygons. These four datasets were submitted to principal component analysis (PCA) to reduce multidimensionality. Each dataset derived a new one. Different combinations of predictor variables were tested. A total of 52 models were evaluated by means of error of models, prediction uncertainty and external validation for overall accuracy and Kappa index. The best result was obtained by reducing the number of predictors with the PCA along with information from the buffer around the points. Although Random Forest has been considered a robust spatial predictor model, it was clear it is sensitive to different strategies of selecting training dataset. Effort was necessary to find the best training dataset for achieving a suitable level of accuracy of spatial prediction. To identify a specific dataset seems to be better than using a great number of variables or a large volume of training data. The efforts made allowed for the accurate acquisition of a mapped area 15.5 times larger than the reference area.(AU)

A hydropedological approach to a mountainous Clayey Humic Dystrudept in the Mantiqueira Range, southeastern Brazil

The Mantiqueira Range region is one of the most important headwaters in southeastern Brazil. In this context, the relationship between pedology and hydrology has been debated and analyzed in recent years, contributing to the creation of a multidisciplinary science call hydropedology. Therefore, the aim of this study was to evaluate the hydropedological properties of a mountainous Clayey Humic Dystrudept in the Mantiqueira Range region, in the state of Minas Gerais, Brazil, comparing two land-uses, native forest and pasture. The hydraulic conductivity results demonstrated that native forest (MFO) has a strong influence on this parameter, offering conditions for movement of water in the soil that are more adequate in this profile than in pasture. These results were supported by pore size distribution analyses which showed that soil from native forest has a greater amount of macropores than soil from pasture as well as greater connectivity between the macropores. In general, the MFO site had greater S index values than the micro-catchment taken from pasture, offering favorable physical conditions for the formation of preferential flowpaths in the soil profile and, therefore, better conditions for groundwater recharge. Soil erosion and water quality results confirmed the importance of native forest areas in the interaction between interception of the direct impact of intense precipitation on the soil surface, and hydropedological attributes, such as saturated hydraulic conductivity and porosity.

Knowledge-based digital soil mapping for predicting soil properties in two representative watersheds

The estimation of soil physical and chemical properties at non-sampled areas is valuable information for land management, sustainability and water yield. This work aimed to model and map soil physical-chemical properties by means of knowledge-based digital soil mapping approach as a study case in two watersheds representative of different physiographical regions in Brazil. Two watersheds with contrasting soil-landscape features were studied regarding the spatial modeling and prediction of physical and chemical properties. Since the method uses only one value of soil property for each soil type, the way of choosing typical values as well the role of land use as a covariate in the prediction were tested. Mean prediction error (MPE) and root mean square prediction error (RMSPE) were used to assess the accuracy of the prediction methods. The knowledge-based digital soil mapping by means of fuzzy logics is an accurate option for spatial prediction of soil properties considering: 1) lesser intense sampling scheme; 2) scarce financial resources for intensive sampling in Brazil; 3) adequacy to properties with non-linearity distribution, such as saturated hydraulic conductivity. Land use seems to influence spatial distribution of soil properties thus, it was applied in the soil modeling and prediction. The way of choosing typical values for each condition varied not only according to the prediction method, but also with the nature of spatial distribution of each soil property.

Knowledge-based digital soil mapping for predicting soil properties in two representative watersheds

The estimation of soil physical and chemical properties at non-sampled areas is valuable information for land management, sustainability and water yield. This work aimed to model and map soil physical-chemical properties by means of knowledge-based digital soil mapping approach as a study case in two watersheds representative of different physiographical regions in Brazil. Two watersheds with contrasting soil-landscape features were studied regarding the spatial modeling and prediction of physical and chemical properties. Since the method uses only one value of soil property for each soil type, the way of choosing typical values as well the role of land use as a covariate in the prediction were tested. Mean prediction error (MPE) and root mean square prediction error (RMSPE) were used to assess the accuracy of the prediction methods. The knowledge-based digital soil mapping by means of fuzzy logics is an accurate option for spatial prediction of soil properties considering: 1) lesser intense sampling scheme; 2) scarce financial resources for intensive sampling in Brazil; 3) adequacy to properties with non-linearity distribution, such as saturated hydraulic conductivity. Land use seems to influence spatial distribution of soil properties thus, it was applied in the soil modeling and prediction. The way of choosing typical values for each condition varied not only according to the prediction method, but also with the nature of spatial distribution of each soil property.(AU)

A hydropedological approach to a mountainous Clayey Humic Dystrudept in the Mantiqueira Range, southeastern Brazil

The Mantiqueira Range region is one of the most important headwaters in southeastern Brazil. In this context, the relationship between pedology and hydrology has been debated and analyzed in recent years, contributing to the creation of a multidisciplinary science call hydropedology. Therefore, the aim of this study was to evaluate the hydropedological properties of a mountainous Clayey Humic Dystrudept in the Mantiqueira Range region, in the state of Minas Gerais, Brazil, comparing two land-uses, native forest and pasture. The hydraulic conductivity results demonstrated that native forest (MFO) has a strong influence on this parameter, offering conditions for movement of water in the soil that are more adequate in this profile than in pasture. These results were supported by pore size distribution analyses which showed that soil from native forest has a greater amount of macropores than soil from pasture as well as greater connectivity between the macropores. In general, the MFO site had greater S index values than the micro-catchment taken from pasture, offering favorable physical conditions for the formation of preferential flowpaths in the soil profile and, therefore, better conditions for groundwater recharge. Soil erosion and water quality results confirmed the importance of native forest areas in the interaction between interception of the direct impact of intense precipitation on the soil surface, and hydropedological attributes, such as saturated hydraulic conductivity and porosity.(AU)

Water erosion associated with rainfall patterns in the extreme South of Bahia in eucalyptus post-planting / Erosão hídrica associada a padrões de chuva no extremo Sul da Bahia em pós-plantio de eucalipto

Soil and water losses caused by water erosion represent a risk of environmental damage and loss of soil productivity, with economic, social and environmental consequences. Plant cover is an important ally against water erosion, together with the knowledge of rainfall characteristics. Thus, this study aimed to evaluate the soil and water losses and to determine rainfall patterns in two homogeneous eucalyptus plantations; one in Yellow Argisol, located in Teixeira de Freitas, and another in Humiluvic Spodosol, located in Caravelas, both in the Extreme South of the state of Bahia. Erosion plots were installed, and consisted of three treatments: bare soil, eucalyptus, and native forest. Rainfall data was obtained from an automatic gauging station, with 10 minute registration interval for erosivity (erosivity index EI30) and rainfall pattern analyses. Higher soil losses were observed in Yellow Argisol, and the advanced rainfall pattern was predominant. Eucalyptus minimum tillage was efficient in reducing soil and water losses by water erosion.

As perdas de solo e de água por erosão hídrica representam risco de dano ambiental e redução da produtividade dos solos, sendo uma das principais formas de degradação com consequências econômicas, sociais e ambientais. A cobertura vegetal é um importante aliado no combate à erosão hídrica, assim como o conhecimento das características da chuva. Deste modo, o presente estudo teve como objetivo avaliar as perdas de solo e água e determinar os padrões de chuva em floresta homogênea de eucalipto em Argissolo Amarelo, no município de Teixeira de Freitas, e em Espodossolo Humilúvico, no município de Caravelas, ambas no Extremo Sul da Bahia. Parcelas de perdas de solo foram instaladas envolvendo três tratamentos: solo descoberto, Eucalipto e Mata nativa (área em equilíbrio), em ambas as classes de solo avaliadas. Para a erosividade, obtida pelo índice de erosividade em 30 minutos (EI30), e para os padrões de chuva dos eventos erosivos foram considerados dados pluviométricos obtidos em estação climatológica automatizada, com intervalos de registro de 10 minutos. As maiores perdas de solo foram observadas no Argissolo Amarelo e o padrão de chuva predominante foi o avançado. O cultivo mínimo de eucalipto mostrou-se eficiente na redução das perdas de solo e de água por erosão hídrica.

Soil, water, nutrients and soil organic matter losses by water erosion as a function of soil management in the Posses sub-watershed, Extrema, Minas Gerais, Brazil / Perdas de solo, água, nutrientes e matéria orgânica do solo por erosão hídrica em função do manejo na sub-bacia das Posses, Extrema, MG

Knowledge of the quantity and quality of the material lost by soil erosion due to soil management is a basic need to identify land management zones in catchments. The aim of this study was to investigate the influence of soil management on the quantity and quality of soil material lost by erosion in the Posses sub-watershed, Municipality of Extrema, State of Minas Gerais, Brazil. Water and sediments lost by natural rainfall erosion were sampled from erosion plots located on a Red-Yellow Argisol (PVA) under the following systems: bare soil, subsistence farming (maize/beans/pumpkin/jack-beans/fallow), degraded pasture, well-managed pasture, and reforestation set up in 2013; and in a Litholic Neosol (RL): reforestation set up in 2008, bare soil, and native forest. Ca, Mg, K, P, N and soil organic matter (SOM) contents were determined in sediment and soil samples (at 0-5 cm depth) for the determination of the runoff enrichment ratios. Management influences soil losses more so than water losses. Minor losses were found in reforestation set up in 2013 (soil); in well-managed pasture (water); and in reforestations (nutrients and SOM). These losses tend to stability with time. The general sequence of nutrient losses was N > Ca > Mg > K > P in PVA; and N > Ca > K > Mg > P in RL. Loss rates of SOM and N followed the order: bare soil > subsistence farming > degraded pasture > well-managed pasture >reforestation, in PVA; and bare soil > native forest > reforestation, in Argisol. Reforestation and wellmanagementpasture are effective conservation strategies in order to lower the erosion process in thePosses sub-watershed. Soil losses, as well as nutrients and organic matter losses were more influencedby soil management than water losses. The safeguarding native forest under Argisol is essential to theconservation of this pedoenvironment, especially in steep slopes.(AU)

O conhecimento da quantidade e qualidade de material perdido por erosão hídrica em função do manejo do solo constitui uma necessidade básica para a definição de zonas de manejo em áreas de recarga de água. O objetivo desse trabalho foi verificar a influência do manejo do solo sobre a quantidade e qualidade de material perdido por erosão hídrica na sub-bacia hidrográfica das Posses, Extrema-MG. Para isso, foram coletados água e sedimentos erodidos através de parcelas de erosão, instaladas, sob chuva natural, em Argissolo Vermelho-Amarelo (PVA) nos manejos: solo descoberto, rotação cultural (milho/feijão-de-porco/pousio), pastagens degradada e bem manejada, e reflorestamento implantado em 2013; e em Neossolo Litólico (RL) nos manejos: reflorestamento implantado em 2008, solo descoberto e mata nativa. Nas amostras de sedimentos e de solos (coletadas na profundidade de 0-5 cm) foram determinados os teores de Ca, Mg, K, P, N (NT) e de matéria orgânica do solo (MOS) e com isso, calculada a taxa de enriquecimento de enxurrada. O manejo exerce maior influência nas perdas de solo do que nas perdas de água. Menores perdas foram encontradas no reflorestamento implantado em 2013 (solo), pasto bem manejado (água) e reflorestamentos (nutrientes e matéria orgânica). Há uma tendência de estabilização dessas perdas com o tempo de implantação dos sistemas. A tendência geral das perdas de nutrientesno PVA foi NT > Ca > Mg > K > P; e no Argisol foi de NT > Ca > K > Mg > P. As taxas de perdasde MOS e NT seguem a ordem: solo descoberto > rotação cultural > pasto degradado > pasto bemmanejado > reflorestamento, no PVA; e solo descoberto > mata nativa > reflorestamento, no Argisol. Oreflorestamento e o manejo das pastagens são estratégias conservacionistas que minimizam as perdaspor erosão hídrica na sub-bacia das Posses, Extrema-MG. O manejo exerce maior influencia nas perdas de solo e de materiais a ele relacionados do que nas perdas de água. A manutenção da mata nativa sob...(AU)

Water erosion associated with rainfall patterns in the extreme South of Bahia in eucalyptus post-planting / Erosão hídrica associada a padrões de chuva no extremo Sul da Bahia em pós-plantio de eucalipto

Soil and water losses caused by water erosion represent a risk of environmental damage and loss of soil productivity, with economic, social and environmental consequences. Plant cover is an important ally against water erosion, together with the knowledge of rainfall characteristics. Thus, this study aimed to evaluate the soil and water losses and to determine rainfall patterns in two homogeneous eucalyptus plantations; one in Yellow Argisol, located in Teixeira de Freitas, and another in Humiluvic Spodosol, located in Caravelas, both in the Extreme South of the state of Bahia. Erosion plots were installed, and consisted of three treatments: bare soil, eucalyptus, and native forest. Rainfall data was obtained from an automatic gauging station, with 10 minute registration interval for erosivity (erosivity index EI30) and rainfall pattern analyses. Higher soil losses were observed in Yellow Argisol, and the advanced rainfall pattern was predominant. Eucalyptus minimum tillage was efficient in reducing soil and water losses by water erosion.(AU)

As perdas de solo e de água por erosão hídrica representam risco de dano ambiental e redução da produtividade dos solos, sendo uma das principais formas de degradação com consequências econômicas, sociais e ambientais. A cobertura vegetal é um importante aliado no combate à erosão hídrica, assim como o conhecimento das características da chuva. Deste modo, o presente estudo teve como objetivo avaliar as perdas de solo e água e determinar os padrões de chuva em floresta homogênea de eucalipto em Argissolo Amarelo, no município de Teixeira de Freitas, e em Espodossolo Humilúvico, no município de Caravelas, ambas no Extremo Sul da Bahia. Parcelas de perdas de solo foram instaladas envolvendo três tratamentos: solo descoberto, Eucalipto e Mata nativa (área em equilíbrio), em ambas as classes de solo avaliadas. Para a erosividade, obtida pelo índice de erosividade em 30 minutos (EI30), e para os padrões de chuva dos eventos erosivos foram considerados dados pluviométricos obtidos em estação climatológica automatizada, com intervalos de registro de 10 minutos. As maiores perdas de solo foram observadas no Argissolo Amarelo e o padrão de chuva predominante foi o avançado. O cultivo mínimo de eucalipto mostrou-se eficiente na redução das perdas de solo e de água por erosão hídrica.(AU)

Spatial prediction of soil properties in two contrasting physiographic regions in Brazil

This study compared the performance of ordinary kriging (OK) and regression kriging (RK) to predict soil physical-chemical properties in topsoil (0-15 cm). Mean prediction of error and root mean square of prediction error were used to assess the prediction methods. Two watersheds with contrasting soil-landscape features were studied, for which the prediction methods were performed differently. A multiple linear stepwise regression model was performed with RK using digital terrain models (DTMs) and remote sensing images in order to choose the best auxiliary covariates. Different pedogenic factors and land uses control soil property distributions in each watershed, and soil properties often display contrasting scales of variability. Environmental covariables and predictive methods can be useful in one site study, but inappropriate in another one. A better linear correlation was found at Lavrinha Creek Watershed, suggesting a relationship between contemporaneous landforms and soil properties, and RK outperformed OK. In most cases, RK did not outperform OK at the Marcela Creek Watershed due to lack of linear correlation between covariates and soil properties. Since alternatives of simple OK have been sought, other prediction methods should also be tested, considering not only the linear relationships between covariate and soil properties, but also the systematic pattern of soil property distributions over that landscape.