Particle size distribution and mineralogy of Brazilian Ferralsols: Significance for the structure and hydraulic properties.

The Cerrados Biome is one of the major regions of Brazil with 24% of the Brazilian territory (204.106 ha). It is mainly located in the center of Brazil and corresponds to the whole Central Plateau. About 49% of the soils are Ferralsols and approximately 79.106 ha of these soils are dedicated to agriculture. The main characteristics of Ferralsols are a poor horizonation, a weak development of the macrostructure, and a strong submillimetric granular microstructure

Hydraulic properties of the diagnostic horizon of Latosols of a regional toposequence across the Brazilian Central Plateau.

International audienceThe Brazilian Central Plateau covers about 40% of the Cerrados Biome and represents 24% of the Brazilian territory. The Latosols that correspond to about 40 % of the surface area of the Central Plateau are characterized by a poor horizonation, a weak macrostructure and a strong development of the fine granular structure composed of sub-rounded microaggregates 50 to 300 µm in size. In this study, we analyzed the hydraulic properties of a set of Latosols varying according to their clay content and mineralogy with respect to their location along a regional topossequence across the Brazilian Central Plateau. Ten Latosols (L) were selected on the South American Surface (L1 to L4) and Velhas Surface (L5 to L10) and we studied the properties of their diagnostic horizon (Bw). We measured their bulk density and particle density, and the soil-water retention properties at 1, 6, 10, 33, 300, and 1500 kPa by using the centrifugation method. We also determined the saturated hydraulic conductivity in the field using the Guelph permeameter procedure. Results showed that the total pore volume (Vp) ranged from 0.460 to 0.819 cm3 g-1 and 58.2 % of the variance was explained for by the clay content. According to Balbino et al. (2002), Vp was divided into a volume of intra-microaggregates pores (Vintra) and inter-microaggregates pores (Vinter). Results showed that Vintra ranged from 0.090 to 0.234 cm3 g-1 and Vinter from 0.305 to 0.585 cm3 g-1. Results showed also that Vp explained a proportion of the variance of the water retained that decreased with the water potential. On the other hand, the clay content explained a proportion of that variance that increases when the water potential decreased. The great proportion of variance (90.7 %) explained for by the clay content alone at 1500 kPa showed that there is little variability that can be attributed to clay mineralogy variation. The saturated hydraulic conductivity (Ks) was related to an effective porosity (Φe) defined as the volume proportion of pore with equivalent diameter > 300 µm. Finally, our results showed that water retention properties and saturated hydraulic conductivity varied mainly according to the clay content and development of large pores without any close link with the mineralogy of the clay fraction

Validity of the centrifuge method for determining the water retention properties of tropical soils

International audienceThis study aims at comparing the centrifuge and pressure plate methods when appropriate duration of run is adopted. Samples collected in tropical soils located in Brazil along a 10-km local hydrosequence across the Cerrado-Amazonia transition (set 1) and along a 350-km regional toposequence across the Cerrado region (set 2) were selected to compare and discuss statistically the similarity of the soil-water retention recorded by using the pressure plate and centrifuge methods. The results showed good agreement (R2 = 0.99) for the 1:1 comparison of measured point-wise soil-water content values (set 1) as well as for the fitted soil-water content curves by van Genuchten model using data points obtained with the two methods (set 2). Thus, the centrifuge method should be considered as an appropriate method for determining soil-water retention properties not only for the similar results with the pressure plate method but also for being much less time consuming

Activation Energy of Kaolinite Dehydroxylation of Brazilian Central Plateau Latosols

International audienceThe Brazilian Central Plateau Latosols occurs on Tertiary South American and Velhas planning surfaces. The purpose of this work was to determine activation energy of kaolinite dehydroxylation and its genesis relationships of the Brazilian Central Plateau Latosols

Modelling Bulk Density According to Structure Development: Toward an Indicator of Microstructure Development in Ferralsols.

Ferralsols have a ferralic horizon at some depth between 30 and 200 cm that results from long and intense weathering. Their clay fraction is usually mainly low-activity clay consisting of kaolinite with hematite, goethite and gibbsite in different proportions. Ferralsols show little or no horizonation, and their macrostructure is absent to moderate. On the other hand, they have typically a strong microstructure consisting of microaggregates < 1 mm in size. Because of the lack or small development of macrostructure, porosity of Ferralsols is closely related to the development of microstructure and the assemblage of elementary particles within the microaggregates with a small contribution of large pores resulting from root development and macrofaunal activity. Their physical properties are then closely related to the development of this microstructure. However, there is still no model in the literature that predicts changes of microstructure of these soils using easily accessible soil properties when land-use is modified. The objective of this work was to relate microstructure development to the bulk density (Db) in Ferralsols and then to make possible the use of Db as an indicator of microstructure development

Kaolinite cristalinity index of Latosols as environment indicator of the Brazilian Central Plateau geomorphologic surfaces

International audienceThe Brazilian Central Plateau is constituted of the South American Surface and Velhas Surface geomorphologic surfaces and represents 24% of the Brazilian territory. Latosols cover about 40% of these Surfaces. Kaolinite, gibbsite, goethite and hematite were recognized in different proportions in the clay fraction of Latosols by many authors. The objective of this work was to analyse the kaolinite cristalinity and to discuss its variability according to the Latosol location on the geomorphic Surfaces of the Brazilian Central Plateau

MAPA DE ERODIBILIDADE DOS SOLOS DA BACIA DO RIO JARDIM-DF

This paper aims to elaborate the soil erodibility map (K-factor of Universal Soil Loss Equation) for the Jardim river watershed. The methodology adopted was a simplified mathematical model developed specifically for the study area, which considers only the clay content. Data are from the semi-detailed soil surveys (1:50,000 scale). The spatial distribution of erodibility for each soil class was analyzed separately, defining specific strategies for their representation as the use of average or interpolation of data. The Plinthosol has the highest erodibility, while the Oxisol has the lowest erodibility.O presente trabalho objetiva elaborar o mapa de erodibilidade do solo (fator K da Equação Universal de Perdas do Solo) para a bacia do rio Jardim. A metodologia adotada utiliza um modelo matemático simplificado desenvolvido especificamente para a área de estudo que considera apenas o teor de argila. As informações utilizadas são provenientes do mapa de solos semi-detalhado (escala 1:50.000). Para uma melhor distribuição das informações pedológicas cada classe de solo foi analisada separadamente definindo estratégicas específicas para a sua representação como o emprego do valor médio ou interpolação dos dados. O Plintossolo possui a maior erodibilidade, enquanto que os Latossolos a menor erodibilidade

Mapa de erodibilidade dos solos da Bacia do Rio Jardim-DF

O presente trabalho objetiva elaborar o mapa de erodibilidade do solo (fator K da Equação Universal de Perdas do Solo) para a bacia do rio Jardim. A metodologia adotada utiliza um modelo matemático simplificado desenvolvido especificamente para a área de estudo que considera apenas o teor de argila. As informações utilizadas são provenientes do mapa de solos semi-detalhado (escala 1:50.000). Para uma melhor distribuição das informações pedológicas cada classe de solo foi analisada separadamente definindo estratégicas específicas para a sua representação como o emprego do valor médio ou interpolação dos dados. O Plintossolo possui a maior erodibilidade, enquanto que os Latossolos a menor erodibilidade. ______________________________________________________________________________ ABSTRACTThis paper aims to elaborate the soil erodibility map (K-factor of Universal Soil Loss Equation) for the Jardim river watershed. The methodology adopted was a simplified mathematical model developed specifically for the study area, which considers only the clay content. Data are from the semi-detailed soil surveys (1:50,000 scale). The spatial distribution of erodibility for each soil class was analyzed separately, defining specific strategies for their representation as the use of average or interpolation of data. The Plinthosol has the highest erodibility, while the Oxisol has the lowest erodibility

IDENTIFICAÇÃO DAS ÁREAS VULNERÁVEIS À EROSÃO A PARTIR DO EMPREGO DA EUPS – EQUAÇÃO UNIVERSAL DE PERDAS DE SOLOS NO MUNICÍPIO DE RIACHÃO DAS NEVES – BA.

Due to agricultural expansion in the last decades, there was a considerable reduction of the Brazilian Biomes. The Bioma Cerrado, specifically, has lost 42% of its original vegetation for agricultural activities (SANO et al.,2002) , resulting in irreparable environmental damage depending on the degree of environmental degradation. Therefore the present study is to apply the EUPS - Equation Universal Soil Loss (Wischmeier & Smith, 1978) to qualitatively identify areas susceptible to erosion laminar in the city of Riachão das Neves- BA. The municipality is part of the agricultural hub of the west of Bahia in recent decades witnessed the advancement of agriculture in the region while the reduction of vegetation in places that should be preserved, especially along watercourses, thus accelerating the erosion process. Keywords: USLE, Topographic Factor, Use and Occupation of the Land.Devido à expansão agrícola das últimas décadas, houve uma redução considerável dos Biomas brasileiro. O Bioma Cerrado, especificamente, já perdeu 90% de sua vegetação original para as atividades agrícolas, tendo como consequencia perdas ambientais irreparáveis dependendo do grau de degradação do ambiente. Portanto o presente estudo faz-se a aplicação da EUPS - Equação Universal de Perdas de Solos (Wischmeier &amp; Smith, 1978) para identificar qualitativamente áreas susceptíveis à erosão laminar no município de Riachão das Neves-BA. O município faz parte do polo agrícola do oeste baiano que nas últimas décadas presenciou o avanço da agricultura na região e ao mesmo tempo a redução da vegetação em locais que deveriam estar preservado, principalmente ao longo dos cursos d’água, acelerando assim os processos erosivos

Panorama atual e potencial de aplicação da abordagem dos serviços ecossistêmicos do solo no Brasil

Human pressure on ecosystems has undesirable impacts on human well-being. After the Millennium Project, much interdisciplinary research has been developed worldwide aiming to understand these impacts on ecosystem flows and processes, and to learn about the costs and the benefits of ecosystem services for production. Soil provides many ecosystem services, since its multi-functionality is the basis for food production, water filtration, nutrient cycling, and other goods essential to life. This article presents the main concepts and classifications of soil ecosystem services and of its functions; the indicators and the methods for assessment, modeling, and valuation of ecosystem services; some recent applications to assess and evaluate impacts of agricultural management practices on soil ecosystem services; as well as challenges and opportunities for research and for development of public policies related to agro-environmental sustainability in Brazil. Although the role of soil in supplying ecosystem services is yet undervalued, scientists are gradually recognizing soil processes and functions as fundamental to assess ecosystem services and the effects of land use and management on them. Interdisciplinary approaches to integrate science and public policies are necessary to build governance based on ecosystem services.A pressão humana sobre os serviços ecossistêmicos tem resultado em impactos indesejáveis sobre o bem-estar humano. Com o Projeto Millennium, várias pesquisas interdisciplinares têm sido desenvolvidas em todo o mundo com o objetivo de entender esses impactos sobre os fluxos e os processos dos ecossistemas e internalizar os custos e os benefícios dos serviços ecossistêmicos para a produção. O solo fornece muitos serviços ecossistêmicos, uma vez que sua multifuncionalidade é a base para a produção de alimentos, filtração de água, ciclagem de nutrientes e outros bens essenciais à vida. Este artigo apresenta os principais conceitos e classificações dos serviços ecossistêmicos do solo e de suas funções; os indicadores e os métodos de avaliação, modelagem e valoração dos serviços ecossistêmicos; algumas aplicações recentes para avaliar impactos de práticas de manejo agrícola sobre os serviços ecossistêmicos do solo; bem como os desafios e as oportunidades para a pesquisa e para o desenvolvimento de políticas públicas relacionadas à sustentabilidade agroambiental no Brasil. Apesar de o papel do solo para prestação de serviços ecossistêmicos ainda ser subestimado, os cientistas têm gradualmente reconhecido os processos e as funções do solo como fundamentais para avaliar os serviços ecossistêmicos e os efeitos do uso e manejo da terra sobre eles. Abordagens interdisciplinares que integrem ciência e políticas públicas são necessárias para construir uma governança com base em serviços ecossistêmicos