Marilusa Pinto Coelho Lacerda

Qualidade de um solo sob diferentes usos e sob Cerrado nativo

Sustainable soil use is becoming increasingly relevant given the increase of anthropic activities. In order to evaluate the soil quality, soil samples were collected from five areas: natural Cerrado (reference), native pasture, planted pasture, annual crops under conventional tillage and pine forest. The areas are located in the Federal District, Brazil, in a clayey Red Yellow Latosol (Acrustox). The following soil quality attributes were measured: bulk density, mechanical resistance to penetration, water infiltration rate, organic matter content, cation exchange capacity, carbon of microbial biomass and basal respiration. Based on the obtained data a comparative diagram was drawn and a soil quality index calculated for each type of use. The results showed a close inverse relationship between soil quality and intensity of use to which the areas were submitted. By analyzing these attributes and the establishment of a comparative model it was possible to evaluate the level of soil degradation caused by each type of use in each area.

Relações pedomorfogeológicas nas chapadas elevadas do Distrito Federal

Detailed studies of pedologic characterization, as well as of relationships between pedology, geology and geomorphology are important for the comprehension of the soil distribution in a landscape. The objective of this study was to evaluate the pedomorphogeological relationships in the Chapadas Elevadas of the Distrito Federal, by the chemical, physical, mineralogical and geochemical characterization of the soils found in this landscape compartment. Two representative top-sequences of the pedologic distribution were selected in this geomorphologic unit, whose soils were formed from metasedimentary rocks of the Grupo Paranoa, represented by Red Oxisols (Latosols), Yellow-Red Oxisols and Cambisols. The physical, chemical and mineralogical properties of the Oxisols of the two top-sequences were mostly similar. The color variation in the Oxisols was due to the differentiated Fe oxide mineralogy - predominantly hematite in LV and goethite in LVA. However, the ICP-AES analysis showed similar Fe2O3 levels in Oxisols, indicating a material of origin (metasedimentary rock) with similar geochemical composition. The goethite formation in LVA was related to the geomorphological position of development, on the edges of the plateau, where the water table oscillation resulted in the formation of a lithoplintic horizon, with consequently deficient drainage conditions. The Cambisols were chemically similar to Oxisols, due to the source material, consisting of pre-weathered sedimentary rock. The pedomorphogeological relations showed that the soil distribution in the Chapadas Elevadas of the Distrito Federal is linked to the geomorphologic evolution and regional geology.

Drenagem interna como fator de diferenciação de Latossolos do Distrito Federal

The objective of this work was to determine the influence of soil physicohydric characteristics on Oxisols diagnostic attributes. Morphological, chemical, physical, mineralogical and physicohydric attributes were surveyed in profiles of five Latossolos Vermelhos (Rhodic Haplustox, LV) and of five Latosssolos Vermelho-Amarelos (Typic Haplustox, LVA), considered representative of this kind of Oxisols in Distrito Federal, Brazil. Besides the soil diagnostic attributes characterization, the water-table oscillation was monitored using 2.5-m depth observation wells, during one year. The studied Oxisols were considered chemically and physically similar. However, they differed as to morphological and mineralogical characterization, with the presence of concretionary horizons and goethite in the LVA. Goethite stability in this soils was influenced by the water-table oscillation. The presence of concretionry horizons in LVA caused an internal drainage deficiency, which resulted in lower saturated hydraulic conductivity and lower variation of the water-table levels. Therefore, LVA soils show lower agricultural potential than LV ones, in Distrito Federal. Oxisols physicohydric characteristics have little influence on soil diagnostic attributes, except for iron oxides mineralogy, which show increased contents of goethite in low internal drainage conditions.

MICROPEDOLOGIA DA ALTERAÇÃO EM PERFIS DE SOLOS COM B TEXTURAL NA REGIÃO DE LAVRAS, MINAS GERAIS

In the region of Lavras, Minas Gerais, Brazil, soils profiles with argillic horizons were selected to evaluate the alterations which occurred during the process of soil formation and to investigate pedogenetic characteristics related to the parent material. Within this region, these soils occur on sloping and hilly landscapes. They were selected for this study because they preserve characteristics inherited from the original bedrocks. Three profiles formed from geologic material with different chemical composition were selected: Profile 1 - Red-Yellow Argisol developed from granitic rocks (Granito de Itutinga); Profile 2 - Red Argisol formed from dioritic rocks (Diorito do Rosario); and Profile 3 - Argiluvic Chernosol formed from basic rocks of the Greenstone-Belt of Lavras. Throughout the layers of each profile, from the consolidated bedrock to the solum, studies were carried out (petrographic analyses on the consolidated and weathered bedrock, micromorphological analyses of C, BC horizons and solum) to investigate the processes of soil formation by evaluating weathering reactions and textural features, with the aid of X-ray diffraction analyses to characterize clay mineralogy. Based on the results obtained, the relationships between parent material and pedogenetic processes were assessed and the order of destruction of primary minerals established. The evolution of the alteration processes along the profiles was found to be directly linked to the texture, chemical and mineralogical composition of the parent materials, revealed in the micromorphological characteristics and mineralogical composition of the horizons constituents of each profile, particularly in the argillic horizon.

Tropical Texture Determination by Proximal Sensing Using a Regional Spectral Library and Its Relationship with Soil Classification

The search for sustainable land use has increased in Brazil due to the important role that agriculture plays in the country. Soil detailed classification is related with texture attribute. How can one discriminate the same soil class with different textures using proximal soil sensing, as to reach surveys, land use planning and increase crop productivity? This study aims to evaluate soil texture using a regional spectral library and its usefulness on classification. We collected 3750 soil samples covering 3 million ha within strong soil class variations in Sao Paulo State. The spectral analyses of soil samples from topsoil and subsoil were measured in laboratory (400–2500 nm). The potential of a regional soil spectral library was evaluated on the discrimination of soil texture. We considered two types of soil texture systems, one related with soil classification and another with soil managements. The soil line technique was used to assess differentiation between soil textural groups. Soil spectra were summarized by principal component analysis (PCA) to select relevant information on the spectra. Partial least squares regression (PLSR) was used to predict texture. Spectral curves indicated different shapes according to soil texture and discriminated particle size classes from clayey to sandy soils. In the visible region, differences were small because of the organic matter, while the short wave infrared (SWIR) region showed more differences; thus, soil texture variation could be differentiated by quartz. Angulation differences are on a spectral curve from NIR to SWIR. The statistical models predicted clay and sand levels with R2 = 0.93 and 0.96, respectively. Indeed, we achieved a difference of 1.2% between laboratory and spectroscopy measurement for clay. The spectral information was useful to classify Ferralsols with different texture classification. In addition, the spectra differentiated Lixisols from Ferralsols and Arenosols. This work can help the development of computer programs that allow soil texture classification and subsequent digital soil mapping at detailed scales. In addition, it complies with requirements for sustainable land use and soil management.

Indicadores de qualidade de Latossolo Vermelho sob diferentes usos

The evaluation and monitoring of soil quality, in the micro-drainage basins which contribute directly to the Rio Descoberto reservoir, in the Rio Descoberto drainage b asin, Distrito Federal (DF), Brazil, are necessary, due to its disordered rural occupation. Thus, this study aimed at evaluating the quality indicators of Red Latosol (RL), in micro-drainage basins located in the northern Rio Descoberto drainage basin , under diversified uses and managements: Savannah (SA), reforestation (RF), native pasture (NP), cultivated pasture (CP), agriculture with covered soil (AC) and agriculture with partial soil covering (AP). Soil density (SD) presented the lowest value for SA and the highest one for AP. The CP area showed the highest values for soil resistance to penetration, reflecting the effect of animal trampling. The highest value for organic matter (OM) was 55.5 g kg -1 , in the CP, and the lowest one was observed in the AC (37.5 g kg -1 ), where decomposition processes are favored. The cation exchange capacity varied from 7.80 cmol c dm -3 (NP) to 9.75 cmol c dm -3 (RF), pointing out the liming effect . The values obtained for microbial biomass carbon and basal respiration showed positive effects of the grass root system in the development of microorganisms. Among t he soil quality attributes evaluated, the OM and SD stood out, confirming that a more intensive agricultural activity is directly related to the quality reduction of the RL evaluated.

Transformações mineralógicas ao longo de perfis de alteração pedogenética na região de Lavras (MG)

Na regiao de Lavras (MG), realizou-se a avaliacao das transformacoes mineralogicas ao longo da alteracao pedogenetica em perfis de solos, discriminados pela composicao geoquimica acida, intermediaria e basica do material de origem. Os solos com horizonte B textural foram selecionados para tal estudo, sendo escolhidas as seguintes classes destes solos: Perfil 1 - Argissolo Vermelho-Amarelo distrofico (PVAd), originado por alteracao de rochas do Dominio geologico Granito de Itutinga; Perfil 2 - Argissolo Vermelho eutrofico (PVe), desenvolvido a partir de rochas do Dominio geologico Diorito do Rosario, e Perfil 3 - Chernossolo Argiluvico ferrico (MTf), evoluido a partir de rochas do Dominio geologico Greenstone-belt de Lavras. Ao longo de cada perfil, desde a rocha fresca ate o solum, realizaram-se analises microscopicas para avaliar os processos de alteracao, mediante evolucao das reacoes de transformacao mineralogica, com auxilio da difracao de raios-X na identificacao da mineralogia da fracao argila. O estudo permitiu elaborar a ordem de destruicao intemperica dos minerais primarios e consequente formacao da mineralogia do solo, estabelecendo-se reacoes de transformacoes mineralogicas e caracterizacao dos processos atuantes ao longo da evolucao da alteracao pedogenetica, assim como suas relacoes com o material de origem. As reacoes de transformacao mineralogica esquematizadas indicam que, nos Argissolos estudados, os minerais primarios foram alterados para caulinita, gibbsita e sesquioxidos de ferro, acrescentando-se sesquioxidos de titânio e vermiculita com hidroxi entre camadas no caso do PVe. Persistiram como residuos o quartzo e o feldspato potassico, este ultimo apenas no PVAd. Ja no Chernossolo avaliado, as alteracoes originaram talco, esmectita, caulinita e sesquioxidos de ferro e titânio, nao havendo minerais primarios residuais.

Relações pedomorfogeológicas e distribuição de pedoformas na estação ecológica de águas emendadas, Distrito Federal

The soil distribution model of the landscape of the Distrito Federal (DF) is influenced by the geomorphological partitioning and geological substrate. The in-depth understanding of pedoforms helps in detailed or semi-detailed soil surveys and mapping of a region. The available pedological mapping of the DF, established in 1978, scale 1:100.00, is still the main source of pedological information of the DF, however, often it cannot meet the needs of the various soil studies, due to the low scale. Thus, the purpose of this work was to study the soil-landscape relationships in a toposequence of the Estacao Ecologica de Aguas Emendadas - ESECAE, representative of relations among properties of the relief, parent material and soil classes in areas with presence of the three geomorphological units defined in the Distrito Federal, including the High Plateau unit, and making a pedoforms map in the area, by geoprocessing techniques. The soil distribution in the landscape was evaluated based on the soil genesis, geomorphology and geology relationships. For the development of this work, geological and geomorphological maps available from ESECAE were used, and Digital Terrain Model (DTM) and maps of geomorphological units, slope classes and geoform distribution were elaborated. Through data obtained from literature and field works, with the characterization of representative soil profiles along the toposequence studied, a model of soil-geomorphological relationship was established in the region. This led to the establishment of the relationships between soils and landscape forms and the mapping of pedoforms of the ESECAE. This pedoforms map provides data for detailed and semi-detailed soil surveys and mapping in areas with the presence of the geomorphological units of the Distrito Federal.

Uso das terras da parte norte da bacia do Rio Descoberto, Distrito Federal, Brasil

This work had the objective to evaluate the land use in the northern region of the Environmental Protection Area of Descoberto River, which encompasses the watersheds of the streams Barrocao, Bucanhao and Capao da Onca, accomplished with the support of geoprocessing techniques. A land use map of the area was produced through analysis and treatment of SPOT 4 satellite images, obtained in 2003, using the software ENVI 3.6. Then, the adequation of land use was checked using cross-tabulation between the maps of present and potential use for agriculture, with the software ArcView 8.3, allowing development of a map of land use suitability. The results showed that most of the area has been used under its agricultural potential, characterizing sustainability in the use of the natural resources, particularly of the soils.

Pedogeoquímica em perfis de alteração na região de Lavras (MG). II - elementos menores e elementos das terras raras

The geochemical behavior of trace elements (TE) and rare earth elements (REE) was evaluated in the region of Lavras (MG), during the pedogenetic evolution in soil profiles with argillic horizons differentiated by acid, intermediate and basic compositions of the parent material.Chemical analyses of TE and REE were performed along the profiles and gains and losses were evaluated through mass chemical balance.The study allowed to group the TE into two classes: (a)moderate to high mobility: loss from the consolidated rocks to the solum; and (b)moderate mobility: relative and occasionally real enrichments in the solum.The REE showed a great mobility throughout the evolution of the alteration profiles.