The aim of this study was to evaluate the influence of Inca muña phenolic antioxidants in the reduction of acrylamide (AA) in potato chips. The potatoes were cut into 2 mm thick slices, the addition of antioxidants was evaluated by immersion at atmospheric pressure and by vacuum impregnation (VI) at 80 kPa for 10 min. In both cases, two antioxidant concentrations were used (1 and 2 mg Gallic acid equivalents (GAE) mL-1) and times of 15, 30, 60 and 120 s. The greatest reduction of AA was obtained by VI with 1 mg GAE mL-1 for 120 s (67.4%) and 2 mg GAE mL-1 for 15 s (59.3%); while immersion at atmospheric pressure with 2 mg GAE mL-1 for 30 s and 60 s resulted in reductions of 50.8 and 50.9%, respectively. Besides, the addition of phenolics from Inca muña had no influence on the colour of potato chips. VI treatment resulted in increased amounts of phenolic compounds and antioxidant capacity in the potato chips being the most abundant phenolic compounds hesperidin and luteolin glucoside; while in the control samples phenolic corresponded to chlorogenic acid isomers.

Abstract Inadequate storage conditions can affect the sensory, physicochemical, and functional properties of tropical fruits such as Pouteria lucuma; which is a climacteric fruit, with a pleasant aroma and flavor; Peru being the main producer and exporter of this fruit, postharvest storage conditions have not been studied to maintain its properties. The objective of the research was to evaluate the effect of the storage conditions on the main physicochemical components, primary and secondary metabolites, antioxidant, and hypoglycemic capacity during postharvest ripening, under two storage conditions: ambient (29 °C and 70% RH) and climatic chamber (15 °C and 90% RH). Regarding the physicochemical characteristics, the state of maturity influenced acidity, pH, reducing sugars, starch, dietary fiber, firmness, pulp color and epicarp. In climate-controlled storage, glucose is the only metabolite that increases; while fructose, alcohol sugars and amino acids (Ala and Val), present higher values under ambient conditions; sucrose, organic acids, amino acids (Tyr, Glu, Asp and Thr), β-carotene, total phenolic compounds and total carotenoids were not affected by the type of storage. The measure of antioxidant and hypoglycemic capacity decreased significantly (p < 0,05), showing to be affected only by the state of maturity. The study of the carotenoid profile according to its spectrum (UV-vis) showed the presence of the group of xanthophylls. The results indicate that the state of maturity concerning the storage condition influenced most of the changes studied.

Resumen Condiciones inadecuadas de almacenamiento pueden afectar las características sensoriales, fisicoquímicos y propiedades funcionales en frutos tropicales como Pouteria lúcuma; que es una fruta climatérica, de aroma y sabor agradable; siendo el Perú el principal productor y exportador de esta fruta, no se han estudiado condiciones de almacenamiento postcosecha que permitan mantener sus propiedades. El objetivo de la investigación fue evaluar el efecto de las condiciones de almacenamiento sobre los principales componentes fisicoquímicos, metabolitos primarios y secundarios, capacidad antioxidante e hipoglucemiante durante la maduración postcosecha, en dos condiciones de almacenamiento: ambiente (29 °C y 70% HR) y cámara climatizada (15 °C y 90% HR). Con relación a las características fisicoquímicas, el estado de madurez influyó en la acidez, pH, azúcares reductores, almidón, fibra dietaría, firmeza, color de pulpa y epicarpio. En almacenamiento en cámara climatizada, la glucosa es el único metabolito que se incrementó; mientras que la fructosa, los azúcares alcohol y los aminoácidos (Ala y Val), presentan valores superiores en condiciones ambientales; la sacarosa, ácidos orgánicos, aminoácidos (Tyr, Glu, Asp y Thr), β-caroteno, compuestos fenólicos totales y carotenoides totales no fueron afectadas por el tipo de almacenamiento. La medida de la capacidad antioxidante e hipoglucemiante disminuyeron significativamente (p < 0,05), mostrando ser afectadas solo por el estado de madurez. El estudio del perfil de carotenoides en función de su espectro (UV-vis) mostró presencia del grupo de las xantofilas. Los resultados indicarían que el estado de madurez respecto a la condición de almacenamiento tuvo efecto sobre la mayoría de los cambios estudiados.

RESUMO O estado de Mato Grosso, com uma área de 903 357 km², não possui uma metodologia oficial para estimar a acidez potencial do solo (H + Al), e sua determinação pelo método padrão é onerosa e demorada. O objetivo deste estudo foi comparar os valores estimados de (H + Al) determinados pelo método padrão de acetato de cálcio com os obtidos por três métodos tampão, a saber, tampão Shoemaker, McLean and Pratt (SMP), tampão Sikora e tampão Santa Maria (SMB), considerando amostras das principais classes de solos cultivados no estado de Mato Grosso. Para isso, 196 amostras de solo foram coletadas na camada arável (0-20 cm) em diferentes sistemas agropastoris e nativos adjacentes. Os modelos estatísticos obtidos foram comparados com modelos hipoteticamente inadequados utilizados pelos laboratórios, pois não há calibração para solos no estado. Após as análises laboratoriais, os pares de valores determinados de H+Al e o pH de equilíbrio corresponde de cada solução tampão foram submetidos a análise de correlação e regressão não-linear (p < 0,05). Verificou-se que o método SMB, que não gera resíduos de poluentes no meio ambiente, foi melhor que os métodos Sikora e SMP para substituir o método padrão, usando a equação H + Al (cm 3 c dm-3) = 51.189-25.70 ln (pHSMB) (R2 = 0,88, P < 0,0001). Assim, se os laboratórios usarem equações não calibradas para estimar a acidez potencial do solo, isso implica subestimar ou superestimar a recomendação de calcário, o que pode comprometer a produtividade das culturas no Mato Grosso.

ABSTRACT Mato Grosso, with a total area of 903357 km², does not have an official methodology for estimating soil potential acidity (H + Al), and determination of H + Al using the standard method is onerous and time consuming. The objective of this study was to compare estimated values of H + Al determined using the standard calcium acetate method with those obtained using three buffer methods, namely, the Shoemaker, McLean, and Pratt (SMP) buffer, Sikora buffer, and Santa Maria buffer (SMB) methods, with samples of the main classes of cultivated soils in the state of Mato Grosso. A total of 196 soil samples were collected from the arable layer (0-20 cm) in agropastoral and adjacent native systems. Statistical models were obtained and compared with models used by laboratories that are hypothetically inadequate because there is no calibration for soils in the state. After laboratory analyses, the paired H + Al and equilibrium pH values corresponding to the equilibrium of each buffer solution (SMP buffer, SMB, and Sikora buffer) were subjected to nonlinear regression analysis (P < 0.05). The SMB method, which does not release pollutant residues into the environment, was better than the Sikora and SMP methods for replacing the standard method used in state laboratories for soil analysis, that is, H + Al (cm3 c dm-3) = 51.189 -25.70 ln(pHSMB) (R2 = 0.88, P < 0.0001). Thus, if laboratories use uncalibrated equations to estimate soil potential acidity, the recommended limestone correction will be underestimated or overestimated, which may compromise crop productivity in Mato Grosso.

ABSTRACT The potential mobility of Cd, Cr, Cu, Ni, Pb and Zn in soils severely impacted by inadequate storage of industrial wastes in Rio de Janeiro State (Brazil) was evaluated by applying the Toxicity Characteristic Leaching Procedure (TCLP). This procedure allowed the estimation of toxicity risks for Cd, Cr and Pb. In a contamination hotspot within the study area, the following order of metal concentrations was observed: Pb > Zn > Cu > Ni > Cd > Cr, with significantly higher values than observed for a control site. Decades of soil exposure to wastes implied TCLP results for Pb above 300 mg/L in this hotspot, which exceed the TCLP regulatory threshold in two orders of magnitude, while Cd (up to 0.8 mg/L) and Cr (up to 0.3 mg/L) results were below the respective TCLP thresholds. Surface soil profile analysis (0-30 cm depth) indicates that Pb vertical migration occurs in the hotspot. TCLP concentrations of Pb were up to four orders of magnitude higher than the groundwater quality threshold preconized by Brazilian regulations for this metal (0.01 mg/L), suggesting that downward dispersion of large loadings of anthropogenic Pb is a major concern.

RESUMEN La movilidad potencial de Cd, Cr, Cu, Ni, Pb y Zn en suelos gravemente afectados por el almacenamiento inadecuado de desechos industriales en el estado de Río de Janeiro, Brasil, se evaluó mediante la aplicación del procedimiento de lixiviación con características de toxicidad (TCLP, por sus siglas en inglés). Este procedimiento permitió la estimación de riesgos de toxicidad para Cd, Cr y Pb. En una zona de alta contaminación dentro del área de estudio, se observó el siguiente orden de concentraciones de metales: Pb > Zn > Cu > Ni > Cd > Cr, con valores significativamente más altos que los observados para un sitio de control. Décadas de exposición del suelo a desechos implicaron resultados de TCLP para Pb por encima de 300 mg/L en esta zona, los cuales exceden el umbral regulatorio de TCLP en dos órdenes de magnitud, mientras que los valores de Cd (hasta 0.8 mg/L) y Cr (hasta 0.3 mg/L) estuvieron por debajo de los umbrales de TCLP respectivos. El análisis del perfil del suelo superficial (0-30 cm de profundidad) indica que la migración vertical de Pb se produce en la zona de alta contaminación. Las concentraciones de Pb obtenidas con el TCLP fueron hasta cuatro órdenes de magnitud más altas que el umbral de calidad del agua subterránea recomendado por las regulaciones brasileñas para este metal (0.01 mg/L), lo que sugiere que la dispersión descendente de grandes cargas de Pb antrópico es un problema importante.

This research aimed to evaluate the HPLC-DAD profile of phenolic compounds, their content and antioxidant capacity in hypocotyls extracts of yellow, red and black maca during pre -harvest, harvest and natural post-harvest drying. A significant increase in total phenolic compounds and antioxidant capacity was observed from pre-harvest to natural post-harvest drying in all three ecotypes. During harvest, red maca had the highest concentration of phenolic compounds. HPLC-DAD analysis revealed the prevalence of 11 phenolic compounds, but with different concentrations in each ecotype and in each stage of study, such as six flavanol derivatives (flavan -3-ol), four derivatives of benzoic acid and an o-coumaric acid derivative. Post-harvest drying, under natural conditions, caused a significant loss (yellow maca 89.90%, red maca 82.49% and black maca 66.31%) of phenolic compounds, mainly derived from benzoic and o-coumaric acid, until non-detectable limits, only two flavanol derivatives (flavan-3-ol) tolerated these conditions. The results of the study sugg est improving cultivation techniques and post-harvest management to preserve the content of phenolic compounds.

Este trabajo tuvo como objetivo evaluar el perfil HPLC-PDA de los compuestos fenólicos, su contenido y capacidad antioxidante en los extractos de los hipocótilos de maca amarilla, roja y negra durante las etapas de pre-cosecha, cosecha y secado natural post-cosecha. De la pre-cosecha al secado natural post-cosecha, en los tres ecotipos, se observó un incremento significativo de los compuestos fenólicos totales y su capacidad antioxidante. En la cosecha, la maca roja presentó la mayor concentración de compuestos fenólicos. Los análisis HPLC-PDA revelaron la prevalencia de 11 compuestos fenólicos, pero con diferentes concentraciones en cada ecotipo y en cada etapa de estudio, seis derivados del flavanol (flavan-3-ol), cuatro derivados del ácido benzoico y un derivado del ácido o-cumárico. El secado post-cosecha en condiciones naturales, generó una pérdida significat iva (maca amarilla 89,90%, maca roja 82,49% y maca negra 66,31%) de compuestos fenólicos, principalmente derivados del ácido benzoico y o-cumárico, llegando a límites no detectables, toleraron estas condiciones dos derivados del flavanol (flavan-3-ol). Los resultados del estudio sugieren mejorar el manejo post cosecha para preservar el contenido de compuestos fenólicos.

Abstract: We report a 72-years-old male patient with extensive differentiated thyroid cancer (DTC), who required a tracheostomy and gastrostomy. Considering his clinical condition, risk of aspiration and management of the ostomies, radioiodine (131I) was administered intravenously, using recombinant human thyrotropin (rhTSH) and levothyroxine. The procedure was successful, both clinically and in terms of radioprotection.

RESUMO Áreas contaminadas por metais podem configurar sério risco à saúde pública e ao meio ambiente. Na década de 1980 foi instalado um pátio de estocagem provisória de resíduos industriais perigosos (CENTRES), no município de Queimados, Rio de Janeiro, o que causou um grande impacto ambiental ao solo da região. A legislação brasileira para o diagnóstico de áreas contaminadas limita a extração de metais em solos aos métodos recomendados pela United States Environmental Protection Agency (USEPA) 3050 e 3051A. Entretanto, muitos pesquisadores utilizam o método com água-régia para a extração de metais em solo, mas são escassos estudos que comparem as concentrações de metais extraídos por água-régia e USEPA 3051A. Logo, o objetivo deste trabalho foi avaliar se o método de extração de metais em solos por água-régia é estatisticamente diferente do método USEPA 3051A. Os resultados obtidos revelaram que as concentrações de Cd, Cr, Cu, Ni, Pb e Zn utilizando ambas as extrações (água-régia e USEPA 3051A) foram estatisticamente semelhantes. Também foi possível identificar que as concentrações de Cu, Ni, Pb e Zn foram superiores ao valor de investigação industrial, o que caracteriza essa área como altamente contaminada e solo classe 4.

ABSTRACT Metal contaminated areas lead to environmental and public health risks. In the 1980s, dangerous industrial waste storage was initiated in the CENTRES area in the municipality of Queimados, Rio de Janeiro, Brazil. The inadequate management of these wastes has promoted a large environmental impact to this region’s soils. The Brazilian legislation for diagnostics of contaminated areas limits the extraction of metals on soils to USEPA 3050-B and USEPA 3051-A methods. However, many researchers use the aqua regia method for extracting metals in soil, but there are few studies comparing concentrations of metals extracted by aqua regia and USEPA 3051A. Therefore, the objective of this work was to evaluate if the method of extracting metals in soils by aqua regia is statistically different from US EPA 3051A. The results showed that the Cd, Cr, Cu, Ni, Pb and Zn concentrations using both extractions were statistically similar. It was also observed that Cu, Ni, Pb and Zn concentrations were higher than the industrial investigation value which characterizes this area as highly contaminated and soil class 4.

ABSTRACT The purpose of this study was to evaluate the production of biogas, as well as the biogas production potential resulting from the anaerobic biodigestion of dairy cattle manure under organic (CMOS) and conventional (CMCS) production system. Also, the concentration of thermotolerant coliforms was evaluated after the biodigestion process. Therefore, bench biodigesters prototypes were supplied with CMOS and CMCS for 30 weeks. The experimental design was completely randomized with four repetitions for each treatment. Analysis of total solids (TS), volatile solids (VS), biogas production potential, most probable number (MPN) of thermotolerant coliforms were made. The cumulative biogas production was 6.18 L and 11.15 L, when using the CMOS and CMCS, respectively. Average biogas production potential of CMCS were 0.2; 2.6 and 2.9 L kg-1 substrate, ST and SV added, respectively and for CMOS 0.1; 1.4 and 1.9 L kg-1substrate, ST and SV added, respectively. After the anaerobic biodigestion process of CMOS and CMCS, it was observed that the concentrations of thermotolerant coliforms were well below than the limit established by law.

Abstract The loquat cultivar Golden Nugget (leaves, flowers and fruits), which has potential commercial importance in Chile, was analyzed for targeted bioactive composition (total phenolic contents: TPC, phenolic profiles and triterpenic acids) and in vitro bioactivity such as antioxidant capacity (AC) and inhibitory activity against enzymes relevant for hyperglycemia (α-amylase and α-glucosidase) and hypertension (angiotensin I-converting enzyme, ACE-I) management. Leaves and flowers had higher TPC and AC than fruits and hydroxycinnamic acid derivatives were found in all structures by HPLC. Chlorogenic acid and quercetin derivatives were detected only in leaves and flowers, which also inhibited the α-amylase and α-glucosidase enzymes, but flowers showed the highest anti-hyperglycemia activity. No inhibition of ACE-I and hyperglycemia-relevant enzymes were found in loquat fruits; additionally, TPC and AC were high at the green stage. Loquat leaves and flowers are sources of phenolic bioactives with potential for diet-based hyperglycemia management. No triterpenic acids were found in any of the loquat parts.

Resumen El cultivar de níspero Golden Nugget (hojas, flores y frutos), el cual presenta un potencial comercial importante para Chile, fue analizado en su composición en compuestos bioactivos (contenido de fenólicos totales: TPC, perfil de fenólicos y ácidos triterpénicos) y bioactividad in vitro como capacidad antioxidante (AC) y actividad inhibitoria de las enzimas relevantes para el control de la hiperglicemia (α-amilasa and α-glucosidasa) y la hipertensión (enzima convertidora de la angiotensina-I, ACE-I). Las hojas y flores tuvieron mayores contenidos de TPC y AC que las frutas y se encontraron principalmente derivados de ácidos hidroxicinámicos en todas las estructuras por HPLC. Solo se detectó ácido clorogénico y derivados de quercetina en las hojas y flores, las cuales inhibieron las enzimas α-amilasa and α-glucosidasa, aunque las flores mostraron la mayor actividad antihiperglicémica. Las frutas no mostraron inhibición de la ACE-I ni actividad antihiperglicémica, sin embargo los TPC y la AC fueron mayores en el estado verde de madurez. Las hojas y flores del cultivar de níspero evaluado constituyen fuentes de fenólicos bioactivos con potencial para el manejo de la hiperglicemia. No se encontraron ácidos triterpénicos en todas las estructuras evaluadas.

Em alguns modelos educacionais atuais (tais como modelos baseados em competência atualmente em voga) é considerado o estilo de aprendizagem do aluno como parte do conjunto de ferramentas para construir estratégias de aprendizagem, no entanto, quando a concepção e implementação de tais estratégias destinam a satisfazer as necessidades das unidades de aprendizagem, não é geralmente levam em conta o comportamento e as reações experimentado pelos alunos em diferentes estilos. Neste trabalho, o sistema 4MAT de estilos de aprendizagem é utilizado para estudar o comportamento dos alunos em Engenharia de Sistemas, particularmente no assunto da física, de acordo com a sua combinação particular de estilos de aprendizagem. Rejeição ou aceitação de diferentes estratégias de aprendizagem aplicados em um ciclo que inclui atividades para todos os quatro estilos de aprendizagem propostos por 4MAT.

Some of the current educational models considers the students' learning style as part of the set of tools for building learning strategies, however when these strategies are designed and implemented with the intention of attend the needs for a session class, the professor does not usually take into account the behavior and reactions experienced by students from different styles. In this work the 4MAT System of learning styles is used to study the behavior for students of Engineering Systems, focusing on the particular case of their physics class, and also according to their particular combination of learning styles. We show rejection or acceptance of different learning strategies applied in a cycle that includes activities for the four learning styles proposed by 4MAT

Dans certains modèles éducatifs actuels ont considère le style d'apprentissage de l'étudiant comme une partie de l'ensemble d'outils qui lui permettent construire des stratégies d'apprentissage; or au moment de la création et la mise en ouvre de ces stratégies, qui ont le but de répondre aux besoins des unités d'apprentissage, habituellement ont ne prend pas en compte le comportement et les réactions des différents types d'élèves. Dans ce travail, on utilise le système de styles d'apprentissage 4MAT pour étudier le comportement des étudiants de l'ingénierie en systèmes, particulièrement dans le cours de physique, en fonction de leur combinaison particulière de styles d'apprentissage. On montre l'acceptation ou le rejet des étudiants sur les différentes stratégies d'apprentissage, appliquées dans un cycle qui comprend des activités pour les quatre styles d'apprentissage proposées par le 4MAT.

En algunos de los modelos educativos actuales se considera el estilo de aprendizaje del estudiante como parte del conjunto de herramientas que permiten construir estrategias de aprendizaje, sin embargo cuando se diseñan e implementan dichas estrategias con la intención de atender las necesidades de las unidades de aprendizaje, no se suele tomar en cuenta el comportamiento y reacciones que experimentan los estudiantes de diferentes estilos. En este trabajo se utiliza el Sistema 4MAT de estilos de aprendizaje para estudiar el comportamiento de estudiantes de Ingeniería en Sistemas, en particular en la asignatura de física, en función de su particular combinación de estilos de aprendizaje. Se muestran los rechazos o aceptación de diferentes estrategias de aprendizaje aplicadas en un ciclo que incorpora actividades para los cuatro estilos de aprendizaje propuestos por el 4MAT.

Nos laboratórios brasileiros, a determinação de micronutrientes para estudos de fertilidade de solos é realizada por extração com solução de Mehlich-1 (M-1), utilizando-se uma razão solo: extrator de 1:5 m/v e posterior quantificação por espectrometria de absorção atômica (AAS). No entanto, muitos laboratórios também empregam razão solo:extrator M-1 de 1:10 m/v para determinar macronutrientes e, ou, quantificar por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES), em substituição ao AAS. Como estudos comparativos entre as concentrações de micronutrientes obtidos por esses métodos alternativos são escassos, o objetivo deste trabalho foi investigar se essas diferentes condições experimentais gerariam diferentes resultados. Os resultados foram estatisticamente tratados e revelaram que as concentrações de Fe e Mn, utilizando-se ambas as razões de solo:extrator M-1 (1:5 e 1:10 m/v) e de Zn, na razão solo:extrator M-1 de 1:10 m/v, foram estatisticamente iguais, enquanto as concentrações de Cu em ambas as razões solo:extrator M-1 e de Zn na razão solo:extrator de 1:5 m/v foram diferentes, quando as duas técnicas de quantificação (ICP OES e AAS) foram comparadas. Também, todas as concentrações de Cu, Fe, Mn e Zn obtidas utilizando razão solo:extrator M-1 de 1:5 m/v foram diferentes daquelas encontradas com a razão de 1:10 m/v, independentemente da técnica de quantificação. A maioria dessas concentrações foi maior quando se usou a razão de 1:5 m/v e alterou a classe de interpretação dos teores. Portanto, não recomenda-se o uso da razão solo:extrator de 1:5 para as extrações dos micronutrientes Cu, Fe, Mn e Zn com solução M-1 de amostras de solo.

In Brazilian laboratories, the determination of micronutrient contents for soil fertility analyses is based on extraction with Mehlich-1 solution (M-1), at a 1:5 w/v soil:extractant ratio, with subsequent quantification by atomic absorption spectrometry (AAS). However, many laboratories also use a 1:10 w/v soil:extractant M-1 ratio for the determination of macronutrients, and/or quantification by optical emission spectrometry with inductively coupled plasma (ICP OES), instead of AAS. As comparative studies between the micronutrient concentrations obtained by these alternative methods are scarce, the aim of this work was to investigate significant differences in results from these different extraction and quantification methods. In this work, statistical analysis showed that the Fe and Mn concentrations using both soil:extractant M-1 ratios (1:5 and 1:10) and Zn concentrations at 1:10 w/v soil: extractant M-1 ratio were similar regardless the quantification equipment. Howeve, the Cu concentrations using both soil:extractant M-1 ratios and the Zn concentrations at 1:5 w/v soil: extractant M-1 ratio differend according to the equipment used to quantifiy these nutrients. Also, all Cu, Fe, Mn and Zn concentrations determined at 1:5 w/v differed from those at 1:10 w/v soil: extractant M-1 ratio, regardless of the quantification technique. Most of these concentrations were higher at a ratio of 1:5 w/v and affected the classification of the contents. It is therefore not recommended to use a soil: extractant ratio of 1:5 for the extraction of the micronutrients Cu, Fe, Mn and Zn from soil samples.

Foram comparadas as concentrações de Na, K e P em extratos de solos, obtidas por um método de extração convencional, no qual é utilizada uma razão solo:extrator (Mehlich-1) de 1:10, com aquelas encontradas utilizando uma razão solo:extrator (Mehlich-1) de 1:5. Também, foram comparados os resultados obtidos por técnicas de quantificação convencionais, nas quais Na e K são quantificados por fotometria de chama e P por espectrofotometria de absorção molecular, com aqueles encontrados por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES). Foram analisadas 15 amostras de solo brasileiro. No estudo de repetibilidade aplicado a todos os resultados, os maiores CVs foram encontrados para P e Na, principalmente quando as concentrações dos analitos foram menores (< 9 mg dm-3 para P e < 10 mg dm-3 para Na). Esse fato foi devido provavelmente à heterogeneidade dos extratos, que continham partículas coloidais. Filtração ou centrifugação em vez de decantação dos extratos provavelmente resultaria em menores CVs. No estudo de reprodutibilidade, realizado para três amostras, foram obtidos resultados não reprodutíveis somente para K em uma amostra. Todos os resultados obtidos por ICP OES foram semelhantes aos obtidos por espectrofotometria de absorção molecular UV-Vis. e fotometria de chama, indicando que a primeira técnica foi adequada para determinação de Na, K e P nos extratos de solos tropicais obtidos com solução de Mehlich-1. Os resultados de Na, K e P obtidos com razão solo:extrator de 1:5 foram estatisticamente diferentes daqueles em que se utilizou razão solo:extrator de 1:10. A maioria dos resultados obtidos com razão solo:extrator de 1:5 foi menor que os obtidos com razão solo:extrator 1:10, sobretudo nas amostras com concentrações de analitos mais elevadas. Portanto, para estudos comparativos envolvendo macronutrientes, deve-se utilizar o método convencional com razão solo:extrator de 1:10.

The Na, K and P concentrations in soil extracts obtained by a conventional extraction method, at a soil:extractant (Mehlich-1) ratio of 1:10, were compared with those found at a soil:extractant (Mehlich-1) ratio of 1:5. Also, the data obtained by conventional quantification techniques, in which Na and K are quantified by flame photometry and P by UV-Vis molecular absorption spectrophotometry, were compared with those found by inductively coupled plasma optical emission spectrometry (ICP OES). Fifteen Brazilian soil samples were analyzed. In the repeatability study applied to all results, the coefficient of variation (CV) was highest for P and Na, mainly when the analyte concentrations were lower (< 9 mg dm-3 for P and < 10 mg dm-3 for Na). This fact was probably due to the heterogeneity of the extracts, which contained colloidal particles. Filtration or centrifugation instead of decantation of the extracts would probably result in lower CV. In the reproducibility study for three samples, non-reproducible results were only obtained for K in a single sample. All ICP OES results were similar to those found by UV-Vis molecular absorption spectrophotometry and flame photometry, indicating that the first technique was adequate for Na, K and P determination in the tropical soil extracts obtained with Mehlich-1 solution. The results for Na, K and P at a soil:extractant ratio of 1:5 were statistically different from those obtained at a ratio of 1:10. Most results obtained at a soil:extractant ratio of 1:5 were lower than at 1:10, mainly in samples with higher analyte concentrations. Therefore, for comparative studies involving macronutrients, the conventional method should be used at a soil:extractant (Mehlich-1) ratio of 1:10.

O objetivo deste trabalho foi avaliar os estoques de C e N do solo e os teores destes elementos na fração leve livre (FLL) da matéria orgânica (MOS) de um Neossolo Quartzarênico, sob diferentes usos agrícolas, no Cerrado. Foram selecionadas cinco áreas para avaliação: cerrado nativo; duas áreas com plantio convencional de soja; uma área ocupada anteriormente com pastagem e convertida em plantio direto de soja; e uma área com pastagem de baixa produtividade. Amostras de solo foram coletadas das camadas de 0-5, 5-10, 10-20 e 20-30 cm de profundidade, para determinação dos estoques de carbono (C) e nitrogênio (N) totais do solo. Os teores destes elementos na FLL foram determinados nas profundidades 0-5 e 5-10 cm. Em comparação à área sob cerrado, foi observado aumento nos estoques de C total do solo nas áreas de soja com até cinco anos de implantação. Houve redução das quantidades de FLL e dos teores de C à profundidade 0-5 cm, nas áreas com plantio de soja e pastagem. Considerando-se o baixo aporte natural de C e N no Neossolo Quartzarênico avaliado, é necessária a adoção de sistemas agrícolas que promovam aporte adequado de resíduos para a manutenção ou incremento da matéria orgânica do solo.

The objective of this work was to evaluate C and N stocks in the soil and their contents in the free light fraction (FLL) of the soil organic matter (MOS), in a Typic Quartzipsamment under different land-use in Cerrado. Five areas were selected for evaluation: native cerrado; two areas with soybean under conventional tillage; one area formerly under pasture and afterwards cultivated with soybean under no-tillage; and one area under pasture with low productivity. Soil samples were collected from 0-5, 5-10, 10-20 and 20-30-cm depth layers to determine total C and N stocks of the soil. Contents of C and N in the FLL were determined at 0-5 and 5-10-cm depth. An increase was observed in the total C stocks in soybean areas implemented until five years, in comparison to the native cerrado area. There was a reduction in the amount of FLL and C content at 0-5 cm depth, in areas with soybean and pasture. Considering the low C and N natural input onto the Typic Quartzipsamment, the adoption of agricultural systems that can promote an adequate supply of residues is necessary for maintaining or increasing the soil organic matter.

O acúmulo de matéria orgânica beneficia a produtividade do solo e reduz a concentração do carbono atmosférico. Entretanto, pouco é sabido a respeito do acúmulo de C e N em solos arenosos cultivados com culturas perenes irrigadas em regiões semi-áridas. O objetivo deste trabalho foi avaliar o efeito do cultivo de fruteiras irrigadas nos estoques de C e N de um Neossolo Quartzarênico em Paraipaba, CE. Foram coletadas amostras na linha e na entrelinha de pomares irrigados de banana, caju, manga, sapoti, goiaba e graviola. Em áreas adjacentes sob vegetação de Caatinga hipoxerófila e após dois anos de desmatamento foram coletadas amostras adicionais. As profundidades de amostragem foram: 0 a 0.1, 0.1 a 0.2 e 0.2 a 0.4 m. Os teores de C e N no solo foram mais altos na camada superficial (0 a 0.1 m). Não houve efeito da profundidade de amostragem sobre a densidade do solo. Os estoques de C e N na área com vegetação de Caatinga na camada de 0 a 0.4 m foram de 27,6 and 2,4 Mg ha-1, respectivamente. A retirada da vegetação natural e o cultivo das fruteiras levaram a reduções de 5 a 23% e 4 a 21% nos estoques de C e N do solo, respectivamente. As culturas do sapoti e da graviola contribuíram para o aumento dos estoques de C e N após a retirada da vegetação natural. As culturas da goiaba, graviola, manga e sapoti contribuíram para a melhoria do índice de estratificação deste solo.

Soil organic matter accumulation provides benefits to soil productivity and reduces atmospheric carbon concentration. However, little is known about the accumulation of C and N by sandy soils under perennial irrigated crops in semiarid regions. The objective of this study was to evaluate the effect of irrigated fruit orchard cultivation on the stocks of soil organic carbon (SOC) and total nitrogen (N) of an Arenosol/Quartzpsament from Paraipaba-CE, Semiarid Brazil. Soil samples were taken from irrigated orchards of banana (Musa ssp.), cashew (Anacardium ocidentale), guava (Psidium guajava), bullock's heart (Annona reticulata), mango (Mangifera indica), and sapote (Manilkara zapota) in the wetted-bulb and non-irrigated area between the plant rows. Additional samples were collected from adjacent areas under secondary Caatinga forest, and under a 2-year-old deforested area. Sampling depths were: 0-0.1, 0.1-0.2, and 0.2-0.4 m. The highest contents of SOC and N were found in the surface layer. The soil bulk density did not change in depth. The stocks of SOC and total N under secondary forest at 0-0.40 m layer were 27.6 and 2.4 Mg ha-1, respectively. Caatinga Forest conversion into fruit orchard cultivation led to a decrease of 5 to 23% and 4 to 21% on SOC and N stocks, respectively. Compared to other soil uses, sapote and bullock's heart contributed for a lower decrease of SOC and N stocks after deforestation. Guava, bullock's heart, mango and sapote contributed for improving the SOC stratification index.