Vinicius de Melo Benites

Soils associated with rock outcrops in the Brazilian mountain ranges Mantiqueira and Espinhaço

A Serra do Espinhaco e a Serra da Mantiqueira sao duas cadeias de grande importância para o Brasil. Nas partes mais altas destas serras encontramse ecossistemas com caracteristicas singulares, associados aos afloramentos rochosos, denominados Complexos Rupestres de Altitude. Esses ambientes apresentam caracteristicas do solo e da vegetacao distintas das areas adjacentes. Os solos sao em geral rasos, arenosos, com alta saturacao de aluminio e teores variados de materia orgânica. Neossolos Litolicos, Cambissolos e Organossolos sao as classes de solo dominantes, diretamente associadas aos afloramentos, formando um mosaico de solos. Alguns solos encontrados nestes ambientes sao endemicos, em funcao das caracteristicas peculiares da rocha matriz, da topografia e da vegetacao, e sua preservacao e estrategica por se tratar de solos raros e ameacados de extincao. A materia orgânica desses solos apresenta alto grau de humificacao, com grande quantidade de fracoes soluveis, e a presenca generalizada de fragmentos de carvao. Horizontes espodicos e rios negros estao tipicamente associados as areas de afloramento de arenito e quartzito, sendo formados pela iluviacao de compostos orgânicos, e sendo menos comuns nas areas de granito. O oligotrofismo destes solos, associado a outras limitacoes de ordem quimica e fisica, induzem o desenvolvimento de estrategias de adaptacao fisiologica e morfologica por parte da vegetacao. A maioria destes ecossistemas e instavel sob a condicao climatica atual, e a intervencao antropica e um fator de aceleracao do processo de degradacao. A descricao detalhada dos solos nestes ambientes e fundamental para um melhor entendimento do seu papel nos processos ecologicos e para o desenvolvimento de politicas de conservacao.

Fracionamento químico da matéria orgânica e características de ácidos húmicos de solos com horizonte a antrópico da amazônia (Terra Preta)

Amazonian dark earth soils that have anthropogenic A horizon (Au) present high natural fertility usually attributed to their high organic matter content and to their higher reactivity. In this study humic substances were quantified and the humic acids (HA) extracted from the 0-20 cm layer of Amazonian dark earth soils (Terra Preta do Indio) under forest and agricultural use were characterized. Adjacent soils with no Au horizon were also investigated. The HA were characterized through the thermogravimetric analysis, elemental composition analysis and characterization of functional groups (total, carboxylic, and phenolic). The A horizon of the anthropogenic soils presented higher total carbon level compared to adjacent soils. Among the humic fractions, the humin was the most abundant. The humic acid fraction (HA) was the dominant among the alkaline soluble fractions. The humic acids of the anthropogenic soils, both under forest and cultivation, showed higher humification degree compared to the non-anthropogenic soils. The agricultural cultivation affected the humic acids stability and reactivity in the anthropogenic soils.

ANÁLISE DOS COMPONENTES PRINCIPAIS E MÉTODOS MULTICRITÉRIO ORDINAIS NO ESTUDO DE ORGANOSSOLOS E SOLOS AFINS

One important property of Organosols (Histosols) (and soils with high content of organic carbon) to predict use potential and degradation risks is the degree of subsidence (loss of mass and volume). In Organosols the subsidence risks vary according to the soil attributes, mainly the nature of organic matter and deposition environment. In this paper we studied 19 soil profiles from different parts of the country, collected and described according to procedures recommended by the SBCS (Brazilian Soil Science Society); the analytical methods proposed by EMBRAPA-Solos were used to characterize the soils. The principal component analysis was used to cluster the profiles based on morphological, physical, chemical and environmental attributes and proved adequate to group the soils under study based on the profile attributes and the grouping was well related to their taxonomy. The soil profiles were ranked by the ordinal multicriteria methods of Border, Condorcet and Copeland based on the subsidence risk. Results indicated a correlation between the methods (with exception of the Condorcet approach, unsuitable to rank the alternatives) and the minimum residue, which is the classical parameter for the evaluation of subsidence, indicating efficacy to rank/classify the soil profiles in relation to subsidence risk. The quantitative approaches used are promising as evaluation tools in soil science studies.

Organic carbon determination in histosols and soil horizons with high organic matter content from Brazil

Soil taxonomy systems distinguish mineral soils from organic soils based on the amount of soil organic carbon. Procedures adopted in soil surveys for organic carbon measurement are therefore of major importance to classify the soils, and to correlate their properties with data from other studies. To evaluate different methods for measuring organic carbon and organic matter content in Histosols and soils with histic horizons, from different regions of Brazil, 53 soil samples were comparatively analyzed by the methods of Walkley & Black (modified), Embrapa, Yeomans & Bremner, modified Yeomans & Bremner, muffle furnace, and CHN. The modified Walkley & Black (C-W & B md) and the combustion of organic matter in the muffle furnace (OM-Muffle) were the most suitable for the samples with high organic carbon content. Based on regression analysis data, the OM-muffle may be estimated from C-W & B md by applying a factor that ranges from 2.00 to 2.19 with 95% of probability. The factor 2.10, the average value, is suggested to convert results obtained by these methods.

Phosphorus quantification in fertilizers using laser induced breakdown spectroscopy (LIBS): a methodology of analysis to correct physical matrix effects

The aim of this study was to develop a quantitative method to determine phosphorus in fertilizers of different matrix compositions using the laser induced breakdown spectroscopy (LIBS) technique. The LIBS spectra were acquired on 26 samples of organic and inorganic fertilizers by using a low cost, portable, gated CCD system in the atmospheric environment. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique. A method was developed to remove the outlier spectra and perform the baseline correction and peak normalization. By applying the proposed corrections, the linear correlation between LIBS and ICP increased from R = 0.76 to R = 0.95. An average error of 15% found in cross-validation of LIBS quantification appeared feasible for P quantification in fertilizers. Two reference samples with different matrix compositions were also analyzed, and the absolute error in the quantification was below 5%. Further, no significant fluctuation was found in P quantification when LIBS was performed over 150 days.

Humic Substance Fractions and Attributes of Histosols and Related High‐Organic‐Matter Soils from Brazil

Abstract Knowledge of the distribution of soil organic matter (SOM) fractions is important in managing soils toward a sustainable agricultural system in a tropical environment. However, data on Histosols is limited. This study developed 19 profiles of Histosols and soils with high organic-matter content from different regions of Brazil. Soil organic matter was fractionated into fulvic acids (FAF), humic acids (HAF), and humin (HUM). The ratios HAF/FAF and AE (alkaline extract)/HUM were calculated. The objectives were to evaluate the method for SOM fractionating in Histosols and related soils and to correlate the distribution of organic fractions with other soil attributes. The humic fractions presented significant correlations with other soil attributes, the best being the correlation between FAF and nutrient level. The HAF and HUM presented high correlation with cationic exchange capacity, active acidity (H+) and pH. Humin and the alkaline extract absorbance measured at 380 nm and 465 nm and presented good correlation with total organic carbon.

Double pulse laser induced breakdown spectroscopy: A potential tool for the analysis of contaminants and macro/micronutrients in organic mineral fertilizers.

Organic fertilizers are obtained from waste of plant or animal origin. One of the advantages of organic fertilizers is that, from the composting, it recycles waste-organic of urban and agriculture origin, whose disposal would cause environmental impacts. Fast and accurate analysis of both major and minor/trace elements contained in organic mineral and inorganic fertilizers of new generation have promoted the application of modern analytical techniques. In particular, laser induced breakdown spectroscopy (LIBS) is showing to be a very promising, quick and practical technique to detect and measure contaminants and nutrients in fertilizers. Although, this technique presents some limitations, such as a low sensitivity, if compared to other spectroscopic techniques, the use of double pulse (DP) LIBS is an alternative to the conventional LIBS in single pulse (SP). The macronutrients (Ca, Mg, K, P), micronutrients (Cu, Fe, Na, Mn, Zn) and contaminant (Cr) in fertilizer using LIBS in SP and DP configurations were evaluated. A comparative study for both configurations was performed using optimized key parameters for improving LIBS performance. The limit of detection (LOD) values obtained by DP LIBS increased up to seven times as compared to SP LIBS. In general, the marked improvement obtained when using DP system in the simultaneous LIBS quantitative determination for fertilizers analysis could be ascribed to the larger ablated mass of the sample. The results presented in this study show the promising potential of the DP LIBS technique for a qualitative analysis in fertilizers, without requiring sample preparation with chemical reagents.

Structural changes in latosols of the cerrado region: II - soil compressive behavior and modeling of additional compaction

Atualmente, ha grande preocupacao com o aumento das areas agricolas degradadas, o que, na maioria das vezes, esta relacionado com a ocorrencia da compactacao do solo. Apesar de a composicao granulometrica do solo ser reconhecidamente importante no comportamento compressivo deste, ha carencia de estudos que quantificam a sua influencia na dinâmica estrutural dos Latossolos oxidicos da regiao do Cerrado. O objetivo deste trabalho foi avaliar as alteracoes estruturais e o comportamento compressivo de Latossolos do municipio de Rio Verde, GO, por meio da modelagem da compactacao adicional do solo. O estudo foi conduzido utilizando-se amostras de cinco Latossolos oxidicos muito contrastantes quanto a textura, sob diferentes condicoes de compactacao do solo. Determinaram-se, a partir de amostras indeformadas coletadas no horizonte Bw dos solos, as curvas de retencao de agua e de compressao do solo, bem como os modelos de capacidade de suporte de carga do solo. Os resultados indicaram que os Latossolos argilosos e muito argilosos estudados, comparativamente aos de textura media, apresentaram elevada suscetibilidade a compactacao. As avaliacoes das curvas de compressao do solo, associadas a valores de densidade do solo de referencia relacionados as funcoes edaficas do solo, permitem a determinacao da pressao benefica ( σb) em termos de retencao de agua e da pressao critica (σcrMAC) capaz de promover a reducao da macroporosidade em niveis considerados criticos para o desempenho das funcoes edaficas do solo. Por sua vez, essas pressoes sao superiores a pressao de preconsolidacao (σp) e, portanto, caracterizadas como compactacao adicional dos Latossolos estudados. Com base no estudo de comportamento compressivo dos Latossolos, e possivel concluir que o uso conjunto dos indices - pressao de preconsolidacao, pressao benefica e pressao critica - permite melhor entendimento do processo de compactacao dos Latossolos oxidicos.

Análise discriminante de solos sob diferentes usos em área de Mata Atlântica a partir de atributos da matéria orgânica

In the mountain region of the State of Rio de Janeiro (Atlantic Rain Forest biome), small farmers practice shifting cultivation in the slash and burn system. In this work, soil surfaces samples (0-15cm) of a Yellow Red Latossolo under five different vegetal coverings (Atlantic Rain Forest, annual culture, coffee, banana and pasture), had been taken in the small farming area of Bom Jardim RJ for soil chemical characterization and carbon content analysis in the different humic fractions. The samples taken under forest and pasture could be clearly isolated from the other groups for the discriminante model created. For the banana, coffee and culture groups, a certain overlapping was observed, indicating a similarity of the soil organic matter attributes between these coverings. The model allowed to correctly classify 88% of the analyzed samples. The fulvic acid (AF), organic carbon (C), total nitrogen (N), and the C/N ratio had been selected by the model, with the fulvic acids having the attribute of higher relative weight. This result suggests that the humic acids fractionation allows the detection of alterations in the soil that are not possible to be identified for the simple determination of the total organic carbon. The discriminate pattern of areas (forest-pasture and banana-coffe-culture) denotes that fertilizer could be related with changes in some important indicator attributes such as fulvic acids.

Distribution of Organic Carbon in the Humic Fractions of Diagnostic Horizons from Brazilian Soils

Abstract This study was developed on 52 soil profiles, 61 surface diagnostic horizons, and 26 subsurface diagnostic horizons classified according to the Soil Taxonomy and Brazilian Soil Classification System (SiBCS) as Mollisols (Chernossolos), Spodosols (Espodossolos), Entisols (Gleissolos), Oxisols (Latossolos), and Histosols (Organossolos). The objective was to quantify the carbon (C) in organic matter fractions and to correlate it with soil chemical attributes. Soil organic matter was fractionated into fulvic acids (C‐FAF), humic acids (C‐HAF), and humin (C‐HUM), and the ratios C‐HAF/C‐FAF and AE (alkaline extract)/C‐HUM were calculated. Humin was the predominant fraction in Mollisols and Oxisols, which showed values of AE/C‐HUM and C‐HAF/C‐FAF lower than 1.0. The humin fraction was also predominant in surface horizons of Spodosols and Entisols, whereas a higher content of C‐FAF and C‐FAH was observed in the subsurface horizons, with values higher than 1.5 for the AE/C‐HUM ratio. C‐HAF was predominant in the Histosols, and C‐HAF/C‐FAF ratio values were higher than 2.0. The highest correlation values with soil attributes were observed for C‐HAF, C‐HUM, and total organic C with pH, sum of bases, and cation exchange capacity. The differences in humic substances distribution was a useful parameter to characterize soil orders in the Brazilian soil classification system and to understand pedogenic processes.