Glenio Guimarães Santos

Macrofauna edáfica associada a plantas de cobertura em plantio direto em um Latossolo Vermelho do Cerrado

The objective of this work was to characterize soil fauna groups and to evaluate the effects of cover crops under no-tillage system, in a Cerrado Oxisol, in two evaluation periods. The cover crops: Crotalaria juncea, Cajanus cajan, Stylosanthes guianensis, Brachiaria brizantha, Brachiaria brizantha/Zea mays association, Pennisetum glaucum, Panicum maximum and Sorghum bicolor were cultivated from November to April of each year. Common bean was sown every September under centre pivot irrigation. The area of each plot was 60 m 2 . Soil monoliths (25x25 cm) were taken randomly from each plot, at 0-10 cm and 10-20 cm dephs, in April and September, 2005, and macrofauna was hand sorted. Identified groups in decreasing order of total density are: Formicidae, Oligochaeta, Dermaptera, Coleoptera, Hemiptera, Miriapoda, Isoptera, Araneae, Lepidoptera, Blattodea and Diptera larvae. Crotalaria juncea showed the highest macrofauna density, followed by B. brizantha, B. brizantha/Zea mays association, Sorghum bicolor, Stylosanthes guianensis, Cajanus cajans, Pennisetum. glaucum, Panicum maximum. The use of cover species in no-tillage system, associated with irrigation, promotes soil colonization by macrofauna.

Propriedades físico-hídricas em Latossolo do Cerrado sob diferentes sistemas de manejo

The objective of this study was to evaluate the physico-hydric soil properties under different management systems in comparison with the native Cerrado, in Santo Antonio de Goias, Goias State, in areas cultivated since 1993. The evaluated systems in the depths of 0 - 0.10 and 0.10 - 0.20 m were: system S1 (soybean/bean/rice/pearl millet /bean), system S2 (soybean/pearl millet/corn), system S3 (corn + Brachiaria brizantha in integrated crop-livestock system) and system S4 (native cerrado). To compare the results obtained in the several soil management systems, the interval of confidence was used, at a probability level of 5%. The use of area under Brachiaria brizantha pasture for animal grazing caused compaction of the soil in the surface layer, verified through the reduction of the macroporosity, and increase of the microporosity and soil bulk density.

Intensidade-duração-frequência de chuvas para o Estado de Mato Grosso do Sul

Rain intensity data are necessary to increase security of hydraulic projects. The objective of this study was to determine the rain storm equations and the spatial distribution of rain intensity for the State of Mato Grosso do Sul, Brazil. The equations were obtained by disaggregation of 24 h rain data from 109 pluviometric stations available in the National Water Agency (ANA) data bank. These equations resulted in coefficients of determination above 0,99 for all localities. The adjusted parameters showed high variability, resulting from different rain intensities in different places of the State. The interpolation of data allowed good visualization of the differences, evidencing higher intensities of rains in the central and northern regions and lower intensities in the southeastern and southwestern regions of the State. These results demonstrated the importance of intensity-duration-frequency relationship and its use for studies and hydraulic projects based on data from each place.

Qualidade física do solo sob sistemas de integração lavoura-pecuária

The objective of this work was to evaluate the physical quality of soil in integrated crop-livestock systems (ICL) in comparison to continuous pasture and native Cerrado. During two years (2005 and 2006), soil samples from a clayed Rhodic Ferralsol were collected from two layers (0-20 and 70-80 cm), in six areas under different crop rotation and ICL. Continuous pasture and native Cerrado were used as reference. The following physical and hydraulic properties were evaluated: bulk density, water saturation, total porosity, macroporosity, effective microporosity, effective saturation, lab and field-saturated hydraulic conductivity, and soil-water retention curve. All the cultivated systems caused impact on the physical and hydraulic properties of the 0-20 cm layer. The continuous pasture provided the best soil physical quality. In the comparison between years, only the soil under conventional tillage had its bulk density increased and its soil porosity decreased. The pasture in the rotation system with ICL, even after four years, does not restore soil physical quality in comparison to continuous pasture.

Chemical dispersants and pre-treatments to determine clay in soils with different mineralogy

Knowledge of the soil physical properties, including the clay content, is of utmost importance for agriculture. The behavior of apparently similar soils can differ in intrinsic characteristics determined by different formation processes and nature of the parent material. The purpose of this study was to assess the efficacy of separate or combined pre-treatments, dispersion methods and chemical dispersant agents to determine clay in some soil classes, selected according to their mineralogy. Two Brazilian Oxisols, two Alfisols and one Mollisol with contrasting mineralogy were selected. Different treatments were applied: chemical substances as dispersants (lithium hydroxide, sodium hydroxide, and hexametaphosphate); pre-treatment with dithionite, ammonium oxalate, and hydrogen peroxide to eliminate organic matter; and coarse sand as abrasive and ultrasound, to test their mechanical action. The conclusion was drawn that different treatments must be applied to determine clay, in view of the soil mineralogy. Lithium hydroxide was not efficient to disperse low-CEC electropositive soils and very efficient in dispersing high-CEC electronegative soils. The use of coarse sand as an abrasive increased the clay content of all soils and in all treatments in which dispersion occurred, with or without the use of chemical dispersants. The efficiency of coarse sand is not the same for all soil classes.

Atributos químicos e estabilidade de agregados sob diferentes culturas de cobertura em Latossolo do cerrado

Objetivou-se, com este trabalho, avaliar o efeito de diferentes culturas de cobertura sobre os atributos quimicos e a estabilidade de agregados de um Latossolo do cerrado, sob plantio direto. O estudo foi conduzido em area experimental na Embrapa Arroz e Feijao, em Santo Antonio de Goias, GO. As culturas de cobertura avaliadas foram: braquiaria, milho em consorcio com braquiaria (integracao lavoura-pecuaria), guandu anao, milheto, capim mombaca, sorgo granifero, estilosantes e crotalaria. As amostras foram coletadas em abril de 2005 e 2006. O delineamento experimental foi o de blocos completos ao acaso com quatro repeticoes e os tratamentos arranjados em esquema fatorial 8 x 2, sendo oito culturas de cobertura e duas profundidades de amostragem do solo: 0-0,10 e 0,10-0,20 m. As culturas de cobertura influenciam, de forma diferenciada, os valores de pH e os teores de calcio, magnesio, aluminio, fosforo, potassio, cobre, zinco e ferro do solo. O tratamento estilosantes tem maior poder em acidificar o solo. A agregacao do solo varia com as culturas de cobertura e com a profundidade.

Equações de intensidade-duração-frequência de chuvas para o estado do Piauí

Neste trabalho objetivou-se ajustar e comparar os parâmetros (K, a, b e c) da equacao de intensidade-duracao-frequencia para precipitacoes pluviais maximas de 133 estacoes pluviometricas localizadas no estado do Piaui, disponiveis no banco de dados da Agencia Nacional de Aguas - ANA. Inicialmente, foi realizada a selecao das estacoes atraves de analise de consistencia das series de dados, a partir do qual foram selecionadas 105 estacoes pluviometricas. As chuvas maximas de um dia foram desagregadas em duracao de 5; 10; 15; 20; 25; 30; 60; 360; 480; 600; 720 e 1.440 minutos e estimadas as chuvas maximas atraves de modelos probabilisticos para cada duracao e periodo de retorno de 5; 10; 25; 50 e 100 anos. Em seguida, fez-se o ajuste dos parâmetros (K, a, b e c) atraves do emprego de regressao linear e nao linear. O ajuste dos parâmetros da equacao de intensidade-duracao-frequencia para precipitacoes maximas realizado por regressao nao linear apresentou R2 (0,99) superior aos valores ajustados por regressao linear (0,98).

Soil use and management systems, time since adoption, and their impacts over aggregation

The Cerrado biome is of notable territorial relevance in the state of Piaui, Brazil. This region is an area of reference for food production. The aim of this work was to evaluate the stability of soil aggregates in water, in function of different soil use and management systems, as well as of the time since adopting these systems in Cerrado areas in the southwest region of Piaui. In this study, nine soil use and management systems were evaluated, arranged in the following manner: no-tillage system of three and six years of use, pasture of two and six years, eucalypt of six and twelve years, conventional tillage of two and eight years, and native Cerrado (Savana). The analyzed variables were: organic carbon, mean geometric diameter, mean weight diameter, aggregate stability index and aggregate diameter classes. Aggregation in Ferralsol is favored by clay and organic carbon contents. The longer adoption time in the no-till, pasture and eucalypt systems favored soil aggregation, while in conventional tillage there was a reduction of the aggregates.

EQUAÇÕES DE INTENSIDADE DE CHUVAS PARA O ESTADO DO MARANHÃO - DOI: 10.13083/1414-3984/reveng.v23n5p435-447

Studies of spatial and temporal distribution of rainfall are of extreme importance for security in planning and execution of hydraulic projects and environmental conservation, so work to determine the intensity-duration-frequency curves of rainfall are indispensable for the planning and construction of hydraulic works. Currently the state of Maranhao provides little information related to the curves of intensity-duration-frequency of rainfall, so studies are necessary to develop the curves for its various municipalities. In this context the objective of this work was to determine the parameters of the intensity-duration-frequency equation for 163 rainfall stations located in the state of Maranhao. Data were obtained from the National Water Agency database. For adjustment of intensity-duration-frequency curves the rainfall breakdown method was used, considering the probabilistic model of Gumbel for estimating the maximum values in different time durations and return period. Upon acquisition of these values the parameters K, a, b and c of the intensity-duration-frequency curves were adjusted by the least squares method. The parameters K, a, b and c of the intensity-duration-frequency curves show good adjust, with 99.7% of curves presenting r2 greater than 0.98.

Indicators of Soil Physical Quality: From Simplicity to Complexity

In working with soil physics, getting new answers to the same questions is a challenge. As soil physicists, we are always hoping to find new ways of understanding such a complex soil science area. In this chapter, we will discuss some of the ways to assess soil physical quality for crop growth, using ascending complexity classification, from the simplest to the more complex soil physical indicators for crop growth.