Gustavo Souza Valladares

Adsorção de fósforo em solos de argila de atividade baixa

ABSTRACT PHOSPHATE SORPTION IN LOW ACTIVITY CLAY SOILS In this study possible correlations between physical and chemical properties and the maximumphosphorus adsorption capacity (MAPC) were evaluated in soils with low activity clay from differentregions of Brazil, using samples from the surface (A) and subsurface (B) horizons of 16 soil profiles. Thedosages for the determination of MAPC were calculated from the level of remaining phosphorus andthey ranged from 0 to 135 mg L -1 . From this data isotherms of P adsorption were built. Correlationswere tested between MAPC and the clay content, organic carbon, ki, kr, specific surface, Al contentdetermined by sulfuric acid attack, and content of different forms of extracted iron. A high variation inthe values of MAPC for the surface horizon (48 to 1429 mg kg -1 ) and for the subsurface horizon (455 to1667 mg kg -1 ) was observed. The correlation coefficients showed a significant association between MAPCand clay content, iron and aluminium determined by sulfuric acid attack and iron extracted by dithionite-citrate-bicarbonate (DCB). The multiple regression analysis showed a good fit to MAPC values based insoil attributes.

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.

Relação entre acidez e outros atributos químicos em solos com teores elevados de matéria orgânica

O elevado teor de materia orgânica dos Organossolos confere-lhes caracteristicas edaficas proprias, que podem ser contrastantes em relacao ao observado em solos minerais. Devido a forte interacao entre a materia orgânica e os elementos a ela adsorvidos, os metodos de rotina em fertilidade do solo podem nao avaliar de forma adequada a acidez nos Organossolos. Os objetivos deste trabalho foram caracterizar e estabelecer relacoes entre atributos do complexo sortivo e a acidez em solos com alto teor de carbono. Foram avaliados doze perfis, onze Organossolos e um Cambissolo, de diferentes Estados brasileiros, coletados de 2000 a 2002. Os perfis foram separados em ambientes de varzeas e planicies litorâneas e solos de ambiente altimontano e planalto. Alem da caracterizacao dos perfis, segundo metodos da Embrapa, o pH foi analisado por diferentes metodos e foram determinados os teores de C, usando um analisador elementar (C_CHN), e a materia orgânica pelo metodo da mufla (MO_mufla). Pelos resultados, verificase que os metodos de determinacao de pH em agua, em KCl e o pH SMP podem ser usados para expressar a acidez desses solos. Observou-se alta correlacao entre o pH SMP e a acidez potencial. Os teores de C_CHN e de MO_mufla tiveram correlacao significativa, porem negativa, com o pH em agua e positiva com os valores T e H. O comportamento diferenciado da acidez dos solos, em funcao do ambiente de formacao, indica ser importante esta separacao no manejo da acidez e na avaliacao da fertilidade em Organossolos.

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.

Comparison of Total Nitrogen Methods Applied for Histosols and Soil Horizons with High Organic Matter Content

Abstract This study was carried out to correlate total nitrogen analyzed by two different methods: Kjeldahl (wet oxidation) and Perkin‐Elmer 2.400 Series II–CHN Mode (dry oxidation or combustion) in Histosols and soil surface horizons with high organic matter content, sampled in different regions of Brazil. A positive correlation (r=0.95**) was verified between the methods, showing that Kjeldahl, because of its simplicity, can be used to routinely determine total nitrogen content in the evaluated soils.

Assessment of heavy metals in soils of a vineyard region with the use of principal component analysis

O manejo agricola com agroquimicos pode levar a contaminacao dos solos por metais pesados. O objetivo deste trabalho foi aplicar a Analise dos Componentes Principais e tecnicas de geoprocessamento para identificar a origem dos metais pesados Cu, Fe, Mn, Zn, Ni, Pb, Cr e Cd como contaminantes potenciais em solos agricolas. O estudo foi desenvolvido em uma area cultivada com vinhedos no Estado de Sao Paulo, Brazil. Amostras de solos foram coletadas e georeferenciadas por GPS sob diferentes usos e coberturas. As concentracoes dos metais nos solos foram obtidas pelo metodo de extracao com DTPA. As concentracoes de Cu e Zn foram consideradas altas na maioria das amostras pesquisadas, sendo maiores nas areas cultivadas com vinhedos sob aplicacoes de fungicidas por decadas. As concentracoes de Cu e Zn apresentaram correlacao. As tecnicas de geoprocessamento e a Analise dos Componentes Principais indicaram enriquecimento do solo com Cu e Zn devido ao uso e manejo dos vinhedos com agroquimicos nas decadas anteriores.

Modelo multicritério aditivo na geração de mapas de suscetibilidade à erosão em área rural

The objective of this work was to evaluate the construction of an erosion susceptibility map for a rural area of the municipality of Guararapes, SP, Brazil, using a multicriteria additive model. Digital maps on the themes relief (declivity and length of the slopes), pedology (obtained at the field), land use and land cover of the region, and interpretation of the digital elevation model were used. The digital maps were treated in a geographic information system environment using the additive multicriteria method and were validated by the universal soil loss equation (USLE) model. Five erosion susceptibility classes were generated: low, moderate, high, very high, and extremely high. The risk map obtained by additive multicriteria had good correspondence with the USLE model. The erosion susceptibility map can be used for the agricultural and environmental planning of the rural area of the municipality of Guararapes.

Substâncias húmicas e suas relações com o grau de subsidência em Organossolos de diferentes ambientes de formação no Brasil 1

The organic matter of soil is part of a dynamic system influenced by several factors, including climate, the content and nature of clays, land use, management and drainage systems, all of which affect the addition rates, and the processes of transformation and evolution of organic compounds. The objective of this study was to quantify and assess the distribution of humic fractions in histosols in different environments and regions of Brazil, relating them to the processes of subsidence. The carbon (C) content in humic substances indicated a predominance of C from the humic-acid fraction (HAF-C of 22.1g kg -1 to 153.7g kg -1 ) in soils from high altitude mountainous regions and upland areas. Possibly the colder climate, coupled with improved fertility, favored the formation of this fraction at the expense of the fulvic acid and humin fractions. On the other hand, the higher humic-acid content makes organosols in these environments more susceptible to the processes of subsidence, especially when under agricultural management. Whereas in flood and coastal-plain environments, there was a greater formation of C from the humin fraction (HUM-C from 79.2 to 267.2g kg -1 ), being the fraction of humic substances most resistant to decomposition. The sum of the humic fractions represented 89% of the total carbon, these two variables being highly correlated. The relationship between alkaline extract and humin (AE / HUM) groups classes of histosols by their formation environment, and is suggested as a diagnostic attribute at the lower levels of the Brazilian System for Soil Classification (SiBCS), allowing differentiation of the histosols as to their potential for subsidence.

Disponibilidade de boro e correlação com propriedades dos solos do Estado do Rio de Janeiro

To correlate extractable boron (B), clay and organic carbon (C) content and soil pH, the contents of available B were determinated in 103 soil samples of surface soil horizons from soils of Rio de Janeiro State, Brazil, using azomethin-H after extraction by hot water method. The average content was 2.43 + 0.67 mg kg-1 of B with a variation from 1.31 to 4.50 mg kg-1. The correlation values between B and organic C (r = 0.29**) and B and clay (r = 0.27**) were both significant. The highest correlation was found between B and pH (r = -0.41**). The amount of available B was influenced by clay and organic C contents.