Daniel Vidal Pérez

Differentiation in the fertility of Inceptisols as related to land use in the upper Solimões river region, western Amazon

The Upper Solimões river region, western Amazon, is the homeland of indigenous populations and contains small-scale agricultural systems that are important for biodiversity conservation. Although traditional slash-and-burn agriculture is being practiced over many years, deforestation there is relatively small compared to other Amazon regions. Pastures are restricted to the vicinity of cities and do not spread to the small communities along the river. Inceptisols are the main soil order (>90%) in the area and have unique attributes including high Al content and high cation exchange capacity (CEC) due to the enrichment of the clay fraction with 2:1 secondary aluminosilicates. Despite its importance, few studies have focussed on this soil order when considering land use effects on the fertility of Amazon soils. Thus, the objective of this study was to evaluate changes in soil fertility of representative land use systems (LUSs) in the Upper Solimões region, namely: primary rainforest, old secondary forest, young secondary forest, agroforestry, pasture and agriculture. LUSs were significantly differentiated by the chemical attributes of their topsoil (0-20 cm). Secondary forests presented soil chemical attributes more similar to primary rainforest areas, while pastures exhibited the highest dissimilarity from all the other LUSs. As a whole, soil chemical changes among Inceptisols dominated LUSs showed patterns that were distinct from those reported from other Amazon soils like Oxisols and Ultisols. This is probably related to the presence of high-activity clays enriched in exchangeable aluminum that heavily influenced the soil chemical reactions over the expected importance of organic matter found in most studies conducted over Oxisol and Ultisol.

Mineralogia, química e micromorfologia de solos de uma microbacia nos tabuleiros costeiros do Espírito Santo

Soils of the coastal plains of the EspIrito Santo state, Brazil, were studied with the objective of investigating and interrelationing their mineralogical, chemical and micromorphological characteristics and to furnish subsides for the pedogenetic environment reconstruction. Eleven soil profiles were described, collected and analysed. Less crystalline Fe by acid ammonium oxalate and amorphous Si by NaOH 0.5 mol L -1 were also determined. On mottles and nodules samples the proportion of hematite and goethite and Al substitution in goethite were analysed. Mineralogical analyses were performed through optical methods, X-ray diffraction and differential thermal analysis. From undisturbed samples of subsuperficial horizons thin sections were prepared for micromorpho- logical analysis. It was found that the present pedogenetic environment is favoring kaolinite stabiliza- tion and goethite formation, removing hematite and being probably responsible for the yellowing (xanthization) of superficial horizons. The process of iron segregation is evidenced by its accumulation in nodules and mottles in relation to soil matrix, probably by diffusion, the source being the matrix. The red nodules and mottles are in process of destruction instead of formation. The iron droplets which frequently occur in the interior of nodules and concretions constitute a stage of the process of develop- ment of these structures.

Separation and determination of molybdenum by inductively coupled plasma optical emission spectrometry using quercetin immobilization on silica gel

Abstract A new method is described for the separation of molybdenum based on its chelation in a column packed with quercetin, immobilized on silica gel in a slightly acidic medium (pH 5.0). Recovery ranged from 95% (NIST 1515 apple leaves) to 99% (deionized, distilled water; DDW) with an absolute blank of 27.5±1.6 pg obtained for the analysis of DDW. Detection limits, absolute and relative, based on a 5.0-ml sample volume were 4.8 pg and 1 ng l −1 , respectively. Results are presented for molybdenum determination in two standard reference materials, NIST 1515 and NIST 1547 peach leaves, using simple calibration curves for quantification. α-Benzoinoxime was used as the eluent.

Disponibilidade de nutrientes no solo, qualidade de grãos e produtividade da soja em solo adubado com lodo de esgoto

O objetivo deste trabalho foi verificar o efeito direto e residual da adubacao com lodo de esgoto, como fonte de P, na produtividade da soja, na qualidade dos graos para consumo humano e no potencial de lixiviacao do nitrato. O experimento foi realizado no campo e constituiu-se dos seguintes tratamentos: ausencia de adubacao quimica e de lodo; adubacao quimica completa; soja com inoculacao mais dose zero de lodo; soja com inoculacao mais 1,5 t ha-1 de lodo; soja com inoculacao mais 3 t ha-1 de lodo; soja com inoculacao mais 6 t ha-1 de lodo; e soja com inoculacao mais adubacao quimica, exceto a nitrogenada. As maiores produtividades de soja, tanto no primeiro como no segundo ano agricola, foram obtidas nas duas maiores doses de lodo. Os teores de varios elementos nos graos de soja, nos tratamentos com lodo, nao diferiram, significativamente, daqueles obtidos nos tratamentos testemunha ou com adubacao mineral. Perdas de NO3- para o ambiente podem ocorrer, principalmente no periodo inicial do ciclo da cultura.

Estimativa da acidez potencial pelo método do pH SMP em solos do estado do Rio de Janeiro

The potential extractable acidity method by Ca(OAc)2 0.5 mol L-1 is widely used in Brazilian soil analysis laboratories. To define the calibration curve between potential extractable acidity and buffered pH SMP, 102 samples of soils from Rio de Janeiro State, Brazil, were analyzed in 1996. The data showed that potential acidity can be estimated by pH SMP buffer suspension (R2 = 0.90**) and that the pH of Ca(OAc)2 0.5 mol L-1 suspension was significantly correlated with the pH SMP.

Caracterização e classificação de plintossolos no Município de Pinheiro-MA

Objetivou-se neste trabalho caracterizar e classificar quatro Plintossolos localizados no municipio de Pinheiro-MA, de forma a validar novas classes propostas no Sistema Brasileiro de Classificacao de Solos (SiBCS). Foram selecionados quatro pedons em pontos distintos da paisagem: terco superior, medio, inferior e base da encosta, tendo como material de origem arenitos ferruginosos da Formacao Itapecuru e sedimentos coluviais e aluviais. Os perfis foram morfologicamente descritos e os horizontes avaliados quanto as propriedades fisicas, quimicas e mineralogicas. Os tres perfis localizados ao longo da encosta foram classificados como Plintossolos Argiluvicos, e o situado na transicao para a varzea, como Plintossolo Haplico. Tres perfis apresentaram carater concrecionario no perfil de solo, identificando os solos como petroplinticos no quarto nivel categorico. Todos os solos apresentaram carater alitico, indicando ambiente de formacao de solos diferenciado nesta localidade do Estado do Maranhao, que favorece a preservacao de argilominerais de alta atividade juntamente com elevada acidez do solo. As classes inseridas no SiBCS, na ordem dos Plintossolos, se mostraram adequadas para classificar os perfis e contemplam as variacoes relacionadas ao ambiente pedogenetico.

COMPARING TWO METHODS FOR SOIL CARBON AND NITROGEN DETERMINATION USING SELECTED BRAZILIAN SOILS

Considering the increasing need for reliable soil carbon (C) and nitrogen (N) determinations, 19 Brazilian soil samples were selected to compare the results of two methods (a) a modified dichromate wet digestion and Kjeldahl that has been in use by Embrapa in most of Brazilian soil surveys (Embrapas method), and (b) an automated technique based on dry combustion (Perkin-Elmer 2.400 Series II–CHN Mode). Considering that the last method is very much influenced by sample size, two weights were tested (10 and 100 mg). The influence of two particle sizes for both methods (crushed and sieved to pass a 0.177-mm mesh) was also tested. A simple linear regression with the confidence limits for the intercept and slope were used to compare methods. Precision was evaluated by the coefficient of variation (C.V.). The results showed that simple crushing is inadequate for performance analysis by dry combustion mainly for small samples (10 mg), where the precision is also low (19.77% for N and 9.41% for C). The dry combustion method is significantly affected by the use of small samples (10 mg), mainly for N analysis. For finely ground samples (< 0.177 mm), a comparison of the results obtained by dry combustion (100 mg weight sample) and by Embrapas method showed a significant 1:1 relation. Thus the use of correction factor is not necessary.

Atributos químicos, carbono orgânico e substâncias húmicas em Organossolos háplicos de várias regiões do Brasil

The dynamics and properties of soil organic matter (SOM) in mineral soils have been studied for many years. However, under tropical conditions, few studies involve organic soils, the characterization of humic substances (HS), or their relationship with chemical properties related to the agricultural potential of Histosols. The objectives of this study were to characterize chemical properties of Histosols in different Brazilian regions; to quantify soil organic carbon and carbon in the SOM fractions; and to evaluate possible relationships between organic carbon content and soil chemical properties in each environment. The chemical properties were measured and carbon was quantified in the soil samples and the SOM fractions (fulvic acid - C-FAF, humic acid - C-HAF, humin - C-HUM). The ratios C-HAF/C-FAF, C-EA/C-HUM, where C-EA (carbon of the alkaline extract) is equal to the sum of C-FAF+C-HAF, were also evaluated. The acidity of the Histosols was high, base saturation below 50 %, and the cation exchange capacity (CEC) high, although the Ca and Mg levels and sum of bases were high in most profiles. The humic fractions were significantly correlated with different soil properties, such as C-HAF and also C-HUM with N, H+, and CEC. The C-HUM and C-HAF predominated over C-FAF. The C-HAF/C-FAF ratio was reduced in the surface layer of Histosols under intense agricultural use or frequent vegetation burning; the SOM, C-HUM and C-HAF contents were also reduced. The chemical properties and C content in the humic substances reflected the transformation degree of SOM and the changes caused by agricultural use, indicating the vulnerability of Histosols.

Normas DRIS para cupuaçuzeiro cultivado em monocultivo e em sistemas agroflorestais

O objetivo deste trabalho foi avaliar a performance de normas DRIS especificas ou gerais no diagnostico do estado nutricional do cupuacuzeiro (Theobroma grandiflorum), na Amazonia Sul-Ocidental. Amostras foliares de cupuacu foram coletadas de 153 pomares comerciais, com idade entre 5 e 18 anos, cultivados em monocultivo ou em sistemas agroflorestais. Foram geradas normas DRIS especificas para cada sistema de producao e normas gerais, obtidas para o conjunto da populacao monitorada. Na obtencao das normas, foi considerada a relacao nutricional entre N, P, K, Ca, Mg, Fe, Cu, Zn e Mn. A maioria das medias das relacoes bivariadas entre nutrientes e dos diagnosticos produzidos pelas normas DRIS especificas nao diferiu em relacao aos produzidos com o uso da norma DRIS generica. Portanto, a avaliacao do estado nutricional de cupuacuzeiros pode ser realizada com o uso de normas DRIS genericas, que independem do sistema de cultivo.

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.