Bruno Teixeira Ribeiro

Lead sorption and leaching from an Inceptisol sample amended with sugarcane vinasse

A vinhaca e produzida em grandes quantidades pela industria de etanol e de aguardente (cachaca). Embora os efeitos da vinhaca nos atributos do solo sejam bem conhecidos, pouco se sabe sobre eles no comportamento sortivo de chumbo (Pb). Avaliaram-se a sorcao e a lixiviacao de Pb em amostras da camada superficial (0-20 cm) de um Cambissolo Haplico Tb Distrofico tipico (CXbd) sob influencia da vinhaca. Para o ensaio de sorcao, as amostras foram peneiradas em malha de 2 mm, tratadas com vinhaca diluida 20% e 50% e ao natural (100%), empregando agua destilada nas amostras controle. Em seguida, solucoes com 0,05; 0,10; 0,25; 0,50 e 0,75 mmol L-1 de Pb foram adicionadas as amostras de solo. Para o ensaio de lixiviacao, foram preparadas colunas de solo em tubos de PVC de 12 cm de altura e 4 cm de diâmetro interno, contendo 200 g de solo. As doses de vinhaca aplicadas sobre as colunas foram correspondentes a 150 e 300 m3 ha-1. As colunas foram mantidas incubadas com vinhaca por sete dias. Apos esse periodo, foram aplicados sobre cada coluna 5 mL de uma solucao de concentracao 100 mmol L-1 de Pb e, posteriormente, realizadas sucessivas lixiviacoes, coletando-se o percolado para determinacao do teor de Pb. A vinhaca aumentou a capacidade maxima de adsorcao de Pb e sua energia de ligacao com o solo em condicoes de equilibrio (ensaio de sorcao), mas em condicoes de nao equilibrio (ensaio de lixiviacao em colunas), a vinhaca aumentou a lixiviacao de Pb. Com base nesses resultados, atencao especial deve ser dada a areas que estejam recebendo vinhaca ao longo dos anos e que estejam ocasionalmente sujeitas a contaminacao por Pb.

Relationship between raindrops and ultrasonic energy on the disruption of a Haplic Cambisol

The aim of this work was to compare aggregate disruption of undisturbed soil samples by ultrasonic energy to aggregate disruption caused by the energy of simulated raindrops, to provide equations that can describe this relationship, and to evaluate whether aggregate stability, expressed by sonication method, may be used to estimate the effect that raindrops have on undisturbed soil samples. Undisturbed soil samples from A, Bi and C horizons of a Cambisol were submitted to different levels of ultrasonic energy and simulated raindrops. Sieved samples (aggregates) were also submitted to different levels of ultrasonic energy so that both disturbed and undisturbed conditions of samples could be compared. The results showed that the method using ultrasonic energy on undisturbed soil samples can simulate the amount of aggregate disruption of soil due to raindrop impact. Dispersion curves of disturbed samples may not be used to estimate the effect of raindrops on undisturbed soil samples.

Cargas superficiais da fração argila de solos influenciadas pela vinhaça e fósforo

Effects of vinasse, P sorption and the interaction vinasse-phosphorus on zeta potential and point of zero charge (PZC) as well as the effects of vinasse on P sorption on clay-fraction samples from two soils were evaluated. The vinasse and P sorption influenced the surface charge of clay fraction of both soils. Sorption of P increased negative charges from soil particles reducing PZC. These effects were more pronounced when clay fraction was previously treated with vinasse. Vinasse treatment reduced P sorption, probably due to coating of P-adsorption sites and by enhancing the negative charges.

Comparação de distribuições de probabilidade e estimativa da precipitação provável para região de Barbacena, MG

Probabilistic studies involving climatic variables are of extreme importance for farming activities, construction, tourism, among others. Seeking to contribute for the planning of irrigate agriculture, this work had as objectives to compare adjusted probability distribution models to the monthly and decennial historical series and to estimate the probable rainfall for the Barbacena County, Minas Gerais State, Brazil. Rainfall data of December, January and February, from 1942 to 2003, were studied, constituting historical series with 62 years of observations. Daily rainfall depths were added for 10 and 30 days, applying Gama, log-Normal 2 and log-Normal 3 parameters probability distribution models. Probability distributions models, were compared with Qui-square statistical test, at 5% significance level. Probable rainfall was estimated for each period, using the best distribution, which was evaluated based on the smallest Qui-square value, for the probability occurrence levels of 75, 90 and 98%. Gama probability distribution was the most adequate model.

Estabilidade de agregados de um latossolo vermelho tratado com cama de peru

Recentemente, tem ocorrido um grande aumento na producao de aves, com destaque para a carne de peru, motivado pelo aumento das exportacoes e a conquista de novos mercados. Como consequencia, tem sido gerada uma grande quantidade de residuos orgânicos com potencial impacto sobre o ambiente. A cama de peru constitui-se no principal residuo dessa atividade avicola, e uma das formas de sua utilizacao e a sua disposicao em solos como condicionador de suas caracteristicas fisicas e quimicas. Assim, objetivou-se com este trabalho avaliar o efeito da aplicacao da cama de peru na estabilidade de agregados de um Latossolo Vermelho Distrofico tipico, sob pastagem de Brachiaria decumbens, localizado em Uberlândia, no Triângulo Mineiro, Minas Gerais. A cama de peru foi aplicada nas dosagens de: 0 (controle), 1.200, 2.400 e 4.800 kg ha-1 e 2.400 kg ha-1 + adubacao mineral (36 kg ha-1 N, 60 kg ha-1 K2O e 60 kg ha-1de P2O5). As aplicacoes foram realizadas em janeiro de 2004 e o solo amostrado em duas epocas distintas (60 e 210 dias apos aplicacao) nas camadas de 0-20 e 20-40 cm para analise da estabilidade de agregados, avaliada pela percentagem total de agregados, percentagem de agregados maiores que 2mm, menores que 0,25mm e diâmetro medio geometrico (DMG). Nao houve efeito das dosagens de cama de peru aplicadas na agregacao do solo, entretanto, independentemente da dose aplicada houve um aumento na estabilidade de agregados, ao longo do tempo, notadamente na camada de 0-20 cm.

Aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse

Soil aggregation is a very complex issue related to important soil attributes and processes. The aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse were evaluated using ultrasonic energy. Vinasse is an important byproduct of sugarcane industries, intensively applied to soils in Brazil as liquid fertilizer. Samples of two Oxisols and one Ultisol were used in this study. The physical and chemical characterization of soils was performed, and the 1 to 2 mm size aggregates (200 g) were packed in PVC columns (6.0 cm high and 4.0 cm internal diameter) and incubated with sugarcane vinasse under lab conditions for 1, 30 and 60 days. After incubation, aggregates were submitted to levels of ultrasonic energy, and the particle size distribution (53 to 2,000 µm, 2 to 53 µm, and < 2 µm fractions) was quantified. Mathematical equations were used to relate the mass of aggregates in each of these fractions to the applied ultrasonic energy, and parameters related to aggregate stability were then obtained. Soils showed an aggregate-hierarchy resulting in a stepwise breakdown under ultrasonic agitation. Considering this soil-aggregation hierarchy, vinasse contributed even in a short time to the bonding between and within 2 to 53 µm aggregates, mainly in the Oxisols. This may be related to organic compounds present in the vinasse, cementing soil particles. Potassium enrichment of soil samples did not contribute to soil dispersion.

Long-term phosphate fertilization, mycorrhizal inoculation and historical land use influence on soybean growth and P uptake

Phosphorus is a key-nutrient in the fertility management of highly weathered tropical soils. So, this work was carried out with the objective of evaluating the influence of the interaction between P doses, mycorrhizal inoculation and historical land use on soybean growth and P uptake in five Latosols (Oxisols) with contrasting chemical, physical and mineralogical properties under a continuous long-term phosphate fertilization (more than 15 years). The plants were cultivated in 4.5L-plastic pots containing 4 kg of soil in a completely randomized design, four replications and 2x2x2 factorial scheme with two P doses; and with or without mycorrhizal inoculation; and soils cultivated for long periods and non-cultivated (under native vegetation). There were two cultivations of ten weeks each. Shoot dry mass, P content and accumulation in the shoot dry mass were evaluated after each cultivation period. The cultivation history reduced the response to P application and inoculation. The soybean response to inoculation was greater in cultivated soils and when the lower P dose was applied. The soybean response magnitude to these variables was different among the studied Latosols. The mineralogical and chemical attributes of the Latosols were determinants.

Urochloa decumbens growth and P uptake as affected by long-term phosphate fertilization, mycorrhizal inoculation and historical land use in contrasting Oxisols of the Brazilian Cerrado

No manejo da fertilidade de Latossolos brasileiros altamente intemperizados e lixiviados, o P e o macronutriente mais limitante. Assim, conduziu-se um experimento em casa de vegetacao, objetivando-se avaliar a influencia da interacao entre doses de P, inoculacao micorrizica e historico de uso do solo no crescimento de Urochloa decumbens e absorcao de P, em quatro Latossolos com atributos quimicos, fisicos e mineralogicos contrastantes. As plantas foram cultivadas em vasos contendo 4 kg de solo, dispostos em um delineamento inteiramente casualizado, com quatro repeticoes e esquema fatorial 2x2x2: duas doses de P; com e sem inoculacao micorrizica; solos cultivados por longos periodos e nao cultivados (sob vegetacao nativa). Realizaram-se dois cultivos com duracao de 10 semanas cada. Apos cada cultivo avaliaram-se a materia seca da parte aerea, teor e acumulo de P na parte aerea. No primeiro cultivo, maior resposta ao P aconteceu nos solos sob vegetacao nativa em associacao a inoculacao e adicao de P. No segundo cultivo, a inoculacao teve maior efeito em todos os solos, associada a menor dose de P. O aumento do P no solo aumenta a concentracao desse nutriente na parte aerea. A inoculacao nao teve efeito na concentracao e no acumulo de P na parte aerea de Urochloa. O crescimento de Urochloa decumbens foi fortemente influenciado pela interacao entre classe de solo x historico de uso da terra x dose de P x inoculacao.

Electrochemical attributes of water from Cerrado wetlands (Veredas), Triângulo Mineiro region, Brazil

Veredas are wetlands typically found in the Brazilian Cerrado playing important environmental functions. The hydromorphic conditions control important processes and reactions occurring in these environments. The objective of this study was to assess the pH, redox potential (Eh), and electrolytic conductivity (EC) of water from five veredas located in the Triângulo Mineiro region, nearby Uberlândia and Uberaba, Minas Gerais State, Brazil. The pH and EC of water samples (in triplicate) collected in different positions (upper, middle and bottom) of the selected wetlands were monitored monthly from September 2014 to September 2015. Eh was monitored in an incubation experiment using soil samples from the superficial layer (0-20 cm) and subsurface layer (40-70 cm) of the middle position of two of the selected veredas. In general, pH ranged from 3.4 to 6.5 throughout the year. For EC, the values ranged from 1.0 to 67.0 μS cm-1. Most of the year, pH was between 4.2 and 5.1 and EC was around 9.0 μS cm-1. Under laboratory conditions, Eh decreased from oxidic conditions to suboxidic (reduced) conditions. There were no significant differences between the wetlands and soil layers regarding the variation of Eh.

Ultrasonic Aggregate Breakdown of an Oxisol as Affected by Cavitation Intensity

ABSTRACT In the soil aggregate stability analysis using ultrasound, the absorbed energy by soil–water suspension is expressed in J mL−1 or J g−1. However, the same energy (J) can be obtained from different combinations of sonication time and power. We evaluated the effect of four different amplitudes (12, 18, 24, and 30 µm) by varying the sonication time in order to obtain the same total ultrasonic energy applied. Aggregates 4–8 mm size from a Brazilian Acrudox were sonicated using a sonicator probe-type. After each sonication, the soil aggregates were wet-sieved and obtained the oven-dried mass of aggregates (8–2 mm; 2–1 mm; 1–0.5 mm; 0.5–0.25 mm; and <0.25 mm). Different responses on soil aggregate breakdown were observed by varying the amplitude, although the amount of applied energy was the same. This work reinforces the need of description of all experimental conditions for suitable comparison of different results.